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A070545 a(n)=Card( k, 0<k<=n such that k is relatively prime to sigma(k)). 0
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..73.

PROG

(PARI) for(n=1, 100, print1(sum(i=1, n, if(gcd(i, sigma(i))-1, 0, 1)), ", "))

CROSSREFS

Sequence in context: A196165 A138366 A065515 * A254828 A091863 A163296

Adjacent sequences:  A070542 A070543 A070544 * A070546 A070547 A070548

KEYWORD

easy,nonn

AUTHOR

Benoit Cloitre, May 02 2002

STATUS

approved

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Last modified September 21 22:07 EDT 2019. Contains 327283 sequences. (Running on oeis4.)