OFFSET
1,9
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..1000
Omar E. Pol, Illustration: Divisors and pi(x)
MAPLE
MATHEMATICA
With[{nn=90}, #[[1]]-DivisorSigma[0, #[[2]]]&/@Thread[{Differences[Prime[ Range[ nn]]], Range[nn-1]}]] (* Harvey P. Dale, Oct 01 2018 *)
CROSSREFS
KEYWORD
easy,sign
AUTHOR
Omar E. Pol, Jun 28 2009
EXTENSIONS
More terms from R. J. Mathar, Jul 01 2009
STATUS
approved