%I #18 May 19 2026 08:41:56

%S 1,8,12,20,742,513152128

%N Indices of 1's in A350877.

%C This sequence is probably infinite, but may grow extremely rapidly. _Russ Cox_ has checked that there are no further terms below 4.9*10^12. - _N. J. A. Sloane_, Jan 25 2022

%C a(7) > 10^16. - _Benjamin Chaffin_, May 18 2026

%e The 1 at 513152128 is a down-drop from 2^32 at index 513152096 in A350877, 2^32 being 712032365 at index 513152095 plus the prime 3582934931.

%Y Cf. A350877, A350616.

%Y See A362107, A362108 for the chains of powers of 2 that lead to these 1's.

%K nonn,hard,more,changed

%O 1,2

%A _Hans Havermann_, Jan 22 2022