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A165629 Numbers n such that sigma(n)/phi(n) = 25/4, where sigma=A000203, phi=A000010. 1
760, 11020, 18088, 21112, 58206, 65262, 71630, 100280, 123424, 142688, 262276, 303212, 332710, 630344, 679070, 761390, 1265096, 1369120, 1454060, 1454260, 1462552, 1704794, 2185750, 2386664, 2627548, 2783872, 2786056, 2909380, 2927848, 5207680, 5289220 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

A subsequence of A011257. Contains the product m*n of relatively prime (gcd(m,n)=1) terms (m,n) in A068390 x A164648 and in A164646 x A165630.

LINKS

Donovan Johnson, Table of n, a(n) for n = 1..1000

MATHEMATICA

Select[Range[5300000], 4*DivisorSigma[1, #]==25*EulerPhi[#]&] (* Harvey P. Dale, May 09 2012 *)

PROG

(PARI) for( i=1, 1e9, sigma(i)*4-25*eulerphi(i) || print1(i", "))

CROSSREFS

Sequence in context: A247400 A234892 A233879 * A151633 A022051 A107515

Adjacent sequences:  A165626 A165627 A165628 * A165630 A165631 A165632

KEYWORD

nonn

AUTHOR

F. Firoozbakht and M. F. Hasler, Sep 23 2009

STATUS

approved

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Last modified December 8 14:38 EST 2016. Contains 278945 sequences.