login

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).

A285704
a(n) = A285703(n) - n = A000203(A064216(n)) - n.
3
0, 1, 1, 2, 2, 2, 5, 4, 5, 8, 7, 8, 0, 1, 9, 14, 7, 6, 13, 16, 17, 20, 5, 20, 6, 16, 21, 4, 25, 24, 29, 10, 15, 28, 25, 32, 35, 1, 9, 34, -10, 38, 13, 28, 39, 26, 43, 24, 41, 6, 47, 50, 19, 50, 53, 40, 53, 22, 25, 24, -4, 52, -23, 50, 61, 62, 41, -8, 63, 68, 61, 24, 23, 19, 65, 74, 21, 42, 73, 64, 39, 76, 13, 80, 48, 40, 81, -10, 73, 84, 89, 88, 35, 18, -5
OFFSET
1,4
LINKS
FORMULA
a(n) = A285703(n) - n = A000203(A064216(n)) - n.
Sum_{k=1..n} a(k) ~ c * n^2, where c = -1/2 + Product_{p prime} (p^3/((p+1)*(p^2-q(p)))) = 0.3168476756..., where q(p) = prevprime(p) (A151799) if p > 2 and q(2) = 1. - Amiram Eldar, Dec 21 2023
MATHEMATICA
Table[-n + DivisorSigma[1, #] &@ If[n == 1, 1, Apply[Times, FactorInteger[2 n - 1] /. {p_, e_} /; p > 2 :> NextPrime[p, -1]^e]], {n, 95}] (* Michael De Vlieger, Apr 26 2017 *)
PROG
(Scheme) (define (A285704 n) (- (A285703 n) n))
CROSSREFS
KEYWORD
sign
AUTHOR
Antti Karttunen, Apr 26 2017
STATUS
approved