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A070545
a(n) = Card( k, 0<k<=n such that k is relatively prime to sigma(k)).
1
1, 2, 3, 4, 5, 5, 6, 7, 8, 8, 9, 9, 10, 10, 10, 11, 12, 12, 13, 13, 14, 14, 15, 15, 16, 16, 17, 17, 18, 18, 19, 20, 20, 20, 21, 22, 23, 23, 24, 24, 25, 25, 26, 26, 26, 26, 27, 27, 28, 29, 29, 29, 30, 30, 31, 31, 32, 32, 33, 33, 34, 34, 35, 36, 37, 37, 38, 38, 38, 38, 39, 39, 40
OFFSET
1,2
LINKS
MATHEMATICA
Accumulate[Table[Boole[CoprimeQ[n, DivisorSigma[1, n]]], {n, 1, 100}]] (* Amiram Eldar, Apr 30 2022 *)
PROG
(PARI) for(n=1, 100, print1(sum(i=1, n, if(gcd(i, sigma(i))-1, 0, 1)), ", "))
CROSSREFS
Partial sums of A325964.
Sequence in context: A356990 A138366 A065515 * A254828 A091863 A163296
KEYWORD
easy,nonn
AUTHOR
Benoit Cloitre, May 02 2002
STATUS
approved