A067249 Digits of sigma(n) end in phi(n).

1, 6, 84, 112, 141, 294, 1188, 1320, 2508, 4584, 5406, 8850, 14270, 17416, 23320, 31152, 79035, 117576, 125576, 132066, 149877, 160664, 162514, 164024, 167970, 170980, 177744, 184584, 223286, 1119636, 1124592, 1216644, 1481800, 1566920, 1626716

Offset

1,2

Comments

There are only 46 terms up to 10 million. - Harvey P. Dale, Oct 04 2012

Links

Harvey P. Dale and Donovan Johnson, Table of n, a(n) for n = 1..150 (first 46 terms from Harvey P. Dale)

Example

sigma(79035) = 138240 ends in phi(79035) = 38240, so 79035 is a term of the sequence.

Mathematica

(*returns true if a ends with b, false o.w.*) f[a_, b_] := Module[{c, d, e, g, h, i, r}, r = False; c = ToString[a]; d = ToString[b]; e = StringLength[c]; g = StringPosition[c, d]; h = Length[g]; If[h > 0, i = g[[h]]; If[i[[2]] == e, r = True]]; r]; Select[Range[10^5], f[DivisorSigma[1, # ], EulerPhi[ # ]] & ]
dsepQ[n_]:=Module[{ep=EulerPhi[n]}, Mod[DivisorSigma[1, n], 10^ IntegerLength[ ep]]==ep]; Select[Range[250000], dsepQ] (* Harvey P. Dale, Oct 04 2012 *)

Crossrefs

Sequence in context: A186659 A196256 A230491 * A351980 A351178 A350947

Adjacent sequences: A067246 A067247 A067248 * A067250 A067251 A067252

Keyword

base,nonn

Author

Joseph L. Pe, Feb 20 2002

Extensions

More terms from Vladeta Jovovic, Feb 22 2002

Status

approved