A more tricky variation of problem 3737.
Thanks to santa c and unwaxed for the corrections :)
Inspired by a problem by dmwit and the tengen page on Sensei's Library. Yes, I know, this is not tengen...
(;AB[la]AB[lb]AB[lc]AB[md]AW[mc]AW[mb]AW[ma]AB[nd]AB[od]AW[ob]AW[pb]AW[pa]AW[rb]AW[qc]AB[pd]AB[pc]AW[qd]AB[qe]AB[re]AB[rc]AB[nb]AW[nc]AB[na]TR[na]C[Black has played the marked stone and is confident in his board position to obtain what he is looking for. What can white do?]AP[goproblems]
(;W[oa];B[sb]
(;W[ra];B[qb]
(;W[qa];B[rd]C[White is dead!])
(;W[rd];B[sd]C[White is dead!]))
(;W[rd];B[sd]C[Ko. Black was looking for this after o19. Now the whole group may die.])
(;W[qb];B[ra];W[rd];B[sd]C[Ko. Black was looking for this after o19. Now the whole group may die.]))
(;W[sb];B[oc]
(;W[rd]C[White loses four stones but lives in the cornerRIGHT])
(;W[qa];B[rd]C[White is dead!])
(;W[ra];B[qb]C[White is dead!]
(;W[rd]C[];B[sd]C[White is dead!])
(;W[qa]C[];B[rd]C[White is dead!]))
(;W[qb]C[Almost. Although white will live in the corner s16 is a better move.]))
(;W[oc];B[sb]
(;W[rd];B[sd]C[Ko. Black was looking for this after o19. Now the whole group may die.])
(;W[qb];B[ra];W[rd];B[sd]C[Ko. Black was looking for this after o19. Now the whole group may die.])
(;W[ra];B[qb]))
(;W[qb];B[sb]
(;W[rd];B[sd]C[]
(;W[ra];B[oc]
(;W[sc]C[Ko. Black was looking for this after o19. Now the whole group may die.])
(;W[sa]C[White loses four stones but lives in the cornerRIGHT]))
(;W[oc];B[ra]C[Ko. Black was looking for this after o19. Now the whole group may die.]))
(;W[ra];B[oc];W[rd];B[sd]C[]
(;W[sc]C[Ko. Black was looking for this after o19. Now the whole group may die.])
(;W[sa]C[White loses four stones but lives in the cornerRIGHT]))
(;W[oc];B[ra];W[rd];B[sd]C[Ko. Black was looking for this after o19. Now the whole group may die.]))
(;W[qa];B[rd]
(;W[qb];B[sb]C[White is dead!])
(;W[sb];B[oc]C[White is dead!])
(;W[oc];B[sb]C[White is dead!]))
(;W[ra];B[qb]
(;W[qa];B[sb]
(;W[oc];B[rd]C[White is dead!])
(;W[rd];B[sd]C[Ko. Black was looking for this after o19. Now the whole group may die.]))
(;W[sb];B[oc]
(;W[rd]C[];B[sd]C[White is dead!])
(;W[qa]C[];B[rd]C[White is dead!])))
(;W[rd];B[sb]C[]
(;W[oc];B[sd]C[Ko. Black was looking for this after o19. Now the whole group may die.])
(;W[oa];B[sd]C[Ko. Black was looking for this after o19. Now the whole group may die.])
(;W[sc]C[White lives in the corner. RIGHT])
(;W[qb];B[sd]C[Ko. Black was looking for this after o19. Now the whole group may die.]
(;W[ra];B[oc]
(;W[sc]C[Ko. Black was looking for this after o19. Now the whole group may die.])
(;W[sa]C[White loses four stones but lives in the cornerRIGHT]))
(;W[oc];B[ra]C[Ko. Black was looking for this after o19. Now the whole group may die.]))
(;W[ra];B[sd]C[Ko. Black was looking for this after o19. Now the whole group may die.])
(;W[sa];B[ra]
(;W[qb];B[sd]C[Ko. Black was looking for this after o19. Now the whole group may die.])
(;W[sc]C[White lives in the corner. RIGHT]))
(;W[qa];B[sd])
(;W[sd]C[White lives in the corner. RIGHT])
(;W[se]C[White lives in the corner. RIGHT]))
(;W[sc];B[rd]
(;W[oa];B[qb]
(;W[qa];B[qc]
(;W[ra];B[sb])
(;W[sb];B[ra]))
(;W[ra];B[sb]))
(;W[qb];B[oc]
(;W[sb];B[ra])
(;W[ra];B[sb]))
(;W[sb];B[qb];W[qa];B[ra]
(;W[oc];B[qc])
(;W[sa];B[qc])
(;W[qc];B[oc]))))