A015800 - OEIS

A015800

Numbers k such that phi(k) + 9 | sigma(k).

26, 312, 828, 2475, 2520, 4950, 7412, 7942, 10464, 14454, 30952, 89262, 1029632, 3116544, 17721152, 56889152, 538655552, 804839424, 9287924224, 206150959104, 698155922432

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OFFSET

1,1

COMMENTS

a(22) > 10^12. - Donovan Johnson, Feb 28 2012

LINKS

Table of n, a(n) for n=1..21.

MATHEMATICA

Cases[Range[100000],

x_ /; Divisible[DivisorSigma[1, x], EulerPhi[x] + 9] == True] (* David Nacin, Feb 28 2012 *)

Select[Range[1000000], Divisible[DivisorSigma[1, #], EulerPhi[#]+9]&] (* Harvey P. Dale, May 24 2012 *)

CROSSREFS

Sequence in context: A000498 A066912 A359622 * A276285 A232064 A030647

Adjacent sequences: A015797 A015798 A015799 * A015801 A015802 A015803

KEYWORD

nonn

AUTHOR

Robert G. Wilson v

EXTENSIONS

a(9)-a(21) from Donovan Johnson, Feb 28 2012

STATUS

approved