A256356 Composites in base 10 that remain composite in exactly two bases b, 2 <= b <= 10, expansions interpreted as decimal numbers.

33247243, 64037779, 104865433, 130237003, 238561081, 550677781, 947051353, 1013991553, 1246382791, 1343122201, 1607697631, 1609062751, 1632753601, 1788658063, 2203645111, 2364166213, 2393866411, 2480419783, 2518589671, 2544177511, 2668538575, 3029334883

Offset

1,1

Comments

Are there any remaining composites in only one other base?

Links

Sebastian Petzelberger, Table of n, a(n) for n = 1..150

Carlos Rivera, PP&P Puzzle 24: Primes in several bases

Crossrefs

Cf. A052026, A256350, A256351, A256352, A256353, A256354, A256355.

Cf. A038537, A052027-A052033, A084482, A236356.

Sequence in context: A157080 A157081 A015354 * A338607 A153324 A184571

Adjacent sequences: A256353 A256354 A256355 * A256357 A256358 A256359

Keyword

nonn,base,hard

Author

Sebastian Petzelberger, Mar 25 2015

Status

approved