OFFSET
1,2
COMMENTS
If k is in the sequence and p is a prime factor, coprime to k, of 2^k + 3^k, then k*p is in the sequence.
55 = 5 * 11
1971145 = 5 * 11 * 35839
3061355 = 5 * 11 * 55661
109715901845 = 5 * 11 * 35839 * 55661
340799222665 = 5 * 11 * 55661 * 111323
See Known Terms link for additional terms.
From Felix Fröhlich, Jun 29 2017: (Start)
For k in the sequence, A220235(k) = 0.
Subsequence of A045576. (End)
LINKS
Robert Israel and Ray Chandler, Known Terms
A. Velampalli et al., Mathematics StackExchange, Can you prove or disprove that there exist infinitely many integers n such that n^2 divides 2^n+3^n?
EXAMPLE
2^5 + 3^5 = 275 is divisible by 5^2, so 5 is in the sequence.
MAPLE
select(t -> 2&^t + 3&^t mod t^2 = 0, [$1..10^6]);
PROG
(PARI) is(n) = Mod(2, n^2)^n==-3^n \\ Felix Fröhlich, Jun 29 2017
(PARI) is(n) = Mod(2, n^2)^n+Mod(3, n^2)^n==0 \\ Charles R Greathouse IV, Jun 29 2017
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Robert Israel, Jun 29 2017
EXTENSIONS
a(6)-a(7) confirmed as next terms by Ray Chandler, Jul 02 2017
Known terms updated and moved to a-file by Ray Chandler, Jul 03 2017
STATUS
approved