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A071525 Numbers n such that sigma(phi(n)) = reversal(n). 2
1, 3, 304, 918, 23922, 2388063, 88423222968, 655516144546 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

There are no other terms up to 10^7. - Jason Earls, Jun 04 2002

There are no other terms up to 45*10^7. - Farideh Firoozbakht, Dec 26 2007

There are no other terms up to 10^10. - Donovan Johnson, Oct 24 2013

a(9) > 10^12. - Giovanni Resta, Nov 10 2017

LINKS

Table of n, a(n) for n=1..8.

EXAMPLE

sigma(phi(304)) = 403 = reverse(304).

MATHEMATICA

Select[Range[10^5], DivisorSigma[1, EulerPhi[ # ]] == FromDigits[Reverse[IntegerDigits[ # ]]] &]

CROSSREFS

Cf. A000010, A000203, A135238.

Sequence in context: A226500 A052505 A307020 * A157583 A218361 A085319

Adjacent sequences:  A071522 A071523 A071524 * A071526 A071527 A071528

KEYWORD

base,nonn

AUTHOR

Joseph L. Pe, Jun 02 2002

EXTENSIONS

More terms from Jason Earls, Jun 04 2002

Definition restored by Farideh Firoozbakht, Dec 26 2007

a(7)-a(8) from Giovanni Resta, Nov 10 2017

STATUS

approved

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Last modified May 22 11:06 EDT 2022. Contains 353949 sequences. (Running on oeis4.)