OFFSET
1,1
LINKS
Paolo Xausa, Table of n, a(n) for n = 1..450
FORMULA
a(n) = A139238(n)/2.
MATHEMATICA
Differences[2^Prime[Range[25]]-1]/2 (* Paolo Xausa, Oct 20 2023 *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Omar E. Pol, Apr 19 2008
EXTENSIONS
a(10)-a(21) from Paolo Xausa, Oct 20 2023
STATUS
approved