id:A073255 - OEIS Search Results

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Sum of divisors of n-th composite number.

+0
12

7, 12, 15, 13, 18, 28, 24, 24, 31, 39, 42, 32, 36, 60, 31, 42, 40, 56, 72, 63, 48, 54, 48, 91, 60, 56, 90, 96, 84, 78, 72, 124, 57, 93, 72, 98, 120, 72, 120, 80, 90, 168, 96, 104, 127, 84, 144, 126, 96, 144, 195, 114, 124, 140, 96, 168, 186, 121, 126, 224, 108, 132 (list; graph; listen)

	OFFSET	`1,1`
	FORMULA	`a(n)=A000203[A002808(n)]`
	EXAMPLE	`First composite is 4, sigma[4]=1+2+4=7=a(1).`
	MATHEMATICA	`c[x_] := FixedPoint[x+PrimePi[ # ]+1&, x] Table[DivisorSigma[1, c[w]], {w, 1, 128}]`
	CROSSREFS	`Cf. A000203, A002808, A035004.` `Sequence in context: A031021 A153245 A062730 this_sequence A162194 A145310 A072834` `Adjacent sequences: A073252 A073253 A073254 this_sequence A073256 A073257 A073258`
	KEYWORD	`nonn`
	AUTHOR	`Labos E. (labos(AT)ana.sote.hu), Jul 22 2002`

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Last modified November 25 20:09 EST 2009. Contains 167514 sequences.

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