OFFSET
1,1
COMMENTS
Sequence focuses on the even Pell numbers.
Corresponding Pell numbers are 2, 2378, 4866752642924153522, 5616228332641321147898, 13264095873479197467931567359068050319018, ...
First differences are 8, 40, 8, 48, 120, 24, 40, ...
EXAMPLE
PROG
(PARI) a000129(n) = sum(k=0, n, binomial(n, 2*k+1) * 2^k);
isA000404(n) = {for(i=1, #n=factor(n)~%4, n[1, i]==3 && n[2, i]%2 && return); n && ( vecmin(n[1, ])==1 || (n[1, 1]==2 && n[2, 1]%2))}
for(n=1, 1e3, if(isA000404(a000129(2*n)), print1(2*n, ", ")));
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Altug Alkan, Jan 26 2016
EXTENSIONS
a(9)-a(14) from Jinyuan Wang, Aug 14 2022
STATUS
approved