id:A072918 - OEIS Search Results

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a(n) = p(n) - sigma(n), where p(n) is the least prime greater than sigma(n).

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1, 2, 1, 4, 1, 1, 3, 2, 4, 1, 1, 1, 3, 5, 5, 6, 1, 2, 3, 1, 5, 1, 5, 1, 6, 1, 1, 3, 1, 1, 5, 4, 5, 5, 5, 6, 3, 1, 3, 7, 1, 1, 3, 5, 1, 1, 5, 3, 2, 4, 1, 3, 5, 7, 1, 7, 3, 7, 1, 5, 5, 1, 3, 4, 5, 5, 3, 1, 1, 5, 1, 2, 5, 13, 3, 9, 1, 5, 3, 5, 6, 1, 5, 3, 1, 5, 7, 1, 7, 5, 1, 5, 3, 5, 7, 5, 3, 2, 1, 6 (list; graph; listen)

	OFFSET	`1,2`
	EXAMPLE	`phi(4) = 7 and the least prime > 7 is 11; hence a(4) = 11 - 7 = 4.`
	MATHEMATICA	`a[n_] := Module[{r, p}, p = DivisorSigma[1, n]; r = p + 1; While[ ! PrimeQ[r], r = r + 1]; r - p]; Table[a[i], {i, 1, 100}]`
	CROSSREFS	`Sequence in context: A070668 A072341 A011130 this_sequence A162944 A140582 A062866` `Adjacent sequences: A072915 A072916 A072917 this_sequence A072919 A072920 A072921`
	KEYWORD	`easy,nonn`
	AUTHOR	`Joseph L. Pe (joseph_l_pe(AT)hotmail.com), Aug 11 2002`

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Last modified December 17 13:29 EST 2009. Contains 170826 sequences.

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