id:A071391 - OEIS Search Results

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Least number m such that Sigma[m]+Phi[m]=n or 0 if no such number exists.

+0
2

0, 1, 0, 2, 0, 3, 0, 0, 4, 5, 0, 0, 0, 6, 0, 0, 0, 0, 8, 0, 0, 10, 0, 0, 0, 13, 0, 0, 0, 14, 0, 12, 0, 17, 0, 0, 0, 19, 16, 0, 0, 0, 0, 21, 18, 22, 0, 0, 0, 20, 25, 0, 0, 26, 0, 0, 0, 27, 0, 0, 0, 31, 0, 0, 0, 0, 0, 24, 0, 34, 0, 35, 0, 37, 0, 0, 0, 38, 32, 30, 0, 41, 0, 0, 0, 43, 0, 0, 0, 0, 0, 0 (list; graph; listen)

	OFFSET	`1,4`
	FORMULA	`a(n)=Min{x; A000203(x)+A000010(x)=n} or a(n)=0 if no solution exists.`
	EXAMPLE	`n=256: a(256)=110, sigma[110]=216,phi[110]=40, 216+40=256=n.`
	MATHEMATICA	`f[x_] := DivisorSigma[1, x]+EulerPhi[x] t=Table[0, {100}]; Do[c=f[n]; If[c<101&&t[[c]]==0, t[[c]]=n], {n, 1, 1000000}]; t`
	CROSSREFS	`Cf. A000010, A000203, A065387, A051612, A071391.` `Sequence in context: A035205 A131104 A141701 this_sequence A102390 A127640 A113303` `Adjacent sequences: A071388 A071389 A071390 this_sequence A071392 A071393 A071394`
	KEYWORD	`nonn`
	AUTHOR	`Labos E. (labos(AT)ana.sote.hu), May 23 2002`

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

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