A190358 Least number having exactly two odd prime factors that differ by 2^n.

15, 21, 33, 57, 185, 201, 393, 1841, 5753, 7217, 10265, 12297, 139553, 607577, 98313, 196617, 3801929, 786441, 27790073, 7340081, 35651873, 281022857, 92274809, 721422137, 1375733393, 6509569217, 3892314953, 805306377

Offset

1,1

Links

G. C. Greubel, Table of n, a(n) for n = 1..1000

Example

a(5) = 185 because 185 = 5 * 37 , and 37 - 5 = 32 = 2^5.

Mathematica

f[n_] := Block[{p = 3}, While[! PrimeQ[p] || ! PrimeQ[p + 2^n], p++]; p (p + 2^n)]; Table[f[n], {n, 1, 60}]

Crossrefs

Cf. A190052.

Sequence in context: A179996 A079814 A168354 * A090999 A123912 A346812

Adjacent sequences: A190355 A190356 A190357 * A190359 A190360 A190361

Keyword

nonn

Author

Michel Lagneau, May 09 2011

Status

approved