OFFSET
1,1
LINKS
G. C. Greubel, Table of n, a(n) for n = 1..15
FORMULA
a(n) = A000396(n) + 1.
MATHEMATICA
(# (# + 1))/2 & /@ Select[2^Range[100] - 1, PrimeQ] + 1 (* G. C. Greubel, Oct 24 2016, based on Harvey P. Dale code from A000396 *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Omar E. Pol, Nov 27 2007
STATUS
approved