A106131 Numbers k such that the k-th semiprime == 6 (mod k).

1, 2, 3, 4, 8, 10, 57, 59, 69, 6914, 613376, 613403, 613431, 613432, 613436, 613447, 613453, 613483, 613484, 613507, 613511, 613513, 613516, 613531, 613535, 613541, 613547, 613579, 613580, 613597, 613607, 6384425453, 6384425504, 6384425519, 6384425555

Offset

1,2

Comments

a(42) > 10^12. - Lucas A. Brown, Oct 19 2020

Links

Lucas A. Brown, Table of n, a(n) for n = 1..41

Lucas A. Brown, semiprimemods.py

Example

a(5) = 8 is a term because the 8th semiprime is 22 and 22 == 6 (mod 8).

Mathematica

Module[{sp=Select[Range[10^7], PrimeOmega[#]==2&]}, Flatten[ Position[ Thread[ {sp, Range[ Length[sp]]}], _?(Mod[#[[1]], #[[2]]]==6&), {1}, Heads-> False]]] (* Harvey P. Dale, May 09 2015 *)

Crossrefs

Cf. A001358, A356135.

Sequence in context: A207644 A114854 A127279 * A275646 A279194 A050727

Adjacent sequences: A106128 A106129 A106130 * A106132 A106133 A106134

Keyword

hard,nonn

Author

Shyam Sunder Gupta, May 07 2005

Extensions

a(1)-a(4) and a(32)-a(41) by Lucas A. Brown, Oct 19 2020

Status

approved