A106129 - OEIS

%I #32 Oct 29 2022 04:42:43

%S 1,2,5,37,38,58,61,70,77,613379,613413,613415,613429,613485,613509,

%T 613518,613521,613533,613543,613599,6384425449,6384425459,6384425463,

%U 6384425517,6384425557,6384425574,6384425634

%N Numbers k such that the k-th semiprime == 4 (mod k).

%C a(28) > 10^12. - _Lucas A. Brown_, Oct 18 2020

%C a(28) <= 121769718289846, a(29) <= 121769718289883 and a(38) <= 121769718292241. - _Martin Ehrenstein_, Oct 28 2022

%H Lucas A. Brown, <a href="https://github.com/lucasaugustus/oeis/blob/main/semiprimemods.py">semiprimemods.py</a>

%e a(3) = 5 is a term because the 5th semiprime is 14 and 14 == 4 (mod 5).

%Y Cf. A001358, A357808.

%K hard,more,nonn

%O 1,2

%A _Shyam Sunder Gupta_, May 07 2005

%E a(21)-a(27) by _Lucas A. Brown_, Oct 18 2020

%E a(1), a(2) by _Lucas A. Brown_, Oct 19 2020