A071847 Numbers n such that sigma(n) - sigma(reverse(n)) = phi(n).

1302, 6364, 13902, 30944, 35404, 57356, 88781, 132432, 141372, 183792, 284242, 555093, 806403, 1967262, 5010576, 5568948, 6298446, 7306241, 7496203, 7944911, 8078106

Offset

1,1

Links

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

Example

sigma(1302) - sigma(reverse(1302)) = sigma(1302) - sigma(2031) = 3072 - 2712 = 360 = phi(1302).

Mathematica

r = {}; Do[ If[ DivisorSigma[1, n] - DivisorSigma[1, FromDigits[ Reverse[ IntegerDigits[n]]]] == EulerPhi[n], r = Append[r, n]], {n, 1, 10^7}]; r
Select[Range[81*10^5], DivisorSigma[1, #]-DivisorSigma[ 1, IntegerReverse[ #]] == EulerPhi[#]&] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Aug 08 2020 *)

Crossrefs

Sequence in context: A107521 A226144 A250728 * A014356 A252308 A277772

Adjacent sequences: A071844 A071845 A071846 * A071848 A071849 A071850

Keyword

base,nonn

Author

Joseph L. Pe, Jun 09 2002

Extensions

Edited and extended by Robert G. Wilson v, Jun 11 2002

Status

approved