OFFSET
1,3
LINKS
Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
FORMULA
EXAMPLE
The prime power divisors of 12 are 2, 3, and 4. These are indices 1, 2, and 3 in the list of prime powers, so a(12) = 2^(1-1) + 2^(2-1) + 2^(3-1) = 7.
PROG
(PARI) al(n) = my(r=vector(n), pps=[p| p <- [1..n], isprimepower(p)], p2); for(k=1, #pps, p2=2^(k-1); forstep(j=pps[k], n, pps[k], r[j]+=p2)); r
(Haskell)
a248906 = sum . map ((2 ^) . subtract 2 . a095874) . tail . a210208_row
-- Reinhard Zumkeller, Mar 07 2015
CROSSREFS
KEYWORD
nonn
AUTHOR
Franklin T. Adams-Watters, Mar 06 2015
STATUS
approved