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A185147 Number of times each value of the sigma function occurs. 1
1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 2, 1, 3, 1, 1, 2, 2, 1, 1, 1, 1, 3, 1, 3, 2, 2, 1, 3, 1, 1, 1, 5, 1, 1, 2, 3, 3, 1, 1, 4, 2, 1, 2, 2, 1, 1, 2, 4, 1, 2, 2, 1, 2, 2, 1, 1, 2, 5, 1, 2, 2, 1, 1, 1, 1, 6, 1, 1, 1, 4, 2, 1, 2, 5, 1, 1, 1, 1, 1, 2, 1, 5, 1, 1, 3, 3, 1, 3, 7, 1, 3, 6, 1, 1, 1, 1, 2, 1, 3, 2 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,7

COMMENTS

The possible values of the sigma (sum of divisors) function are in A002191. Value A002191(n) occurs exactly a(n) times. Because sigma(x) >= x+1 (for x>1) with equality only at prime x, we know that for prime p, sigma(p) is the last time p+1 occurs as a value of sigma. This sequence is the same as A054973 without the zero terms.

LINKS

T. D. Noe, Table of n, a(n) for n = 1..10000

MATHEMATICA

Transpose[Sort[Tally[DivisorSigma[1, Range[Prime[PrimePi[200]]]]]]][[2]]

CROSSREFS

Cf. A007370 (numbers for which a(n)=1).

Sequence in context: A228100 A211992 A182937 * A206921 A123529 A140747

Adjacent sequences:  A185144 A185145 A185146 * A185148 A185149 A185150

KEYWORD

nonn

AUTHOR

T. D. Noe, Mar 18 2011

STATUS

approved

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Last modified July 20 16:24 EDT 2019. Contains 325185 sequences. (Running on oeis4.)