OFFSET
1,2
COMMENTS
All terms are even. - Robert Israel, Mar 24 2020
LINKS
Robert Israel, Table of n, a(n) for n = 1..209
EXAMPLE
16 is in the sequence, because S(2^16) = S(65536) = 25 is a perfect square.
MAPLE
sd:= n -> convert(convert(n, base, 10), `+`):
select(t -> issqr(sd(2^t)), [$0..10000]); # Robert Israel, Mar 24 2020
PROG
(PARI) isok(k) = issquare(sumdigits(2^k)); \\ Michel Marcus, Mar 23 2020
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Daniel Starodubtsev, Mar 23 2020
STATUS
approved