OFFSET
0,2
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..80
MathOverflow, Counting matrices of special types, 2015.
FORMULA
a(n) = Sum_{k=0..n} Stirling1(n,k) * 2^(k*(k+1)/2).
MATHEMATICA
Table[Sum[StirlingS1[n, k]*2^Binomial[k+1, 2], {k, 0, n}], {n, 0, 20}] (* G. C. Greubel, Nov 04 2018*)
PROG
(PARI) A259763(n) = sum(k=1, n, stirling(n, k, 1) * 2^(k*(k+1)/2) );
(Magma) [(&+[StirlingFirst(n, k)*2^Binomial(k+1, 2): k in [0..n]]): n in [0..20]]; // G. C. Greubel, Nov 04 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
Max Alekseyev, Jul 04 2015
EXTENSIONS
a(0)=1 prepended by Alois P. Heinz, Jul 12 2015
STATUS
approved