A278257 Least number with the prime signature of A005187(n).

1, 2, 4, 2, 8, 6, 2, 6, 16, 12, 2, 6, 2, 4, 6, 2, 32, 6, 6, 6, 6, 2, 30, 6, 2, 4, 12, 2, 24, 24, 6, 12, 64, 30, 2, 30, 2, 2, 6, 30, 2, 16, 6, 6, 6, 24, 2, 6, 6, 2, 12, 2, 30, 24, 30, 2, 30, 48, 2, 12, 12, 6, 120, 2, 128, 30, 2, 6, 24, 2, 30, 6, 6, 6, 6, 2, 60, 24, 12, 6, 6, 6, 48, 30, 6, 120, 4, 2, 30, 48, 6, 180, 2, 6, 24, 30, 2, 2, 6, 2, 60, 72, 6, 6, 6, 48

Offset

1,2

Links

Antti Karttunen, Table of n, a(n) for n = 1..8193

Formula

a(n) = A046523(A005187(n)).

Mathematica

f[n_] := If[Length@ # == 1 && #[[1, 1]] == 1, {0}, Sort@ #[[All, -1]]] &@ FactorInteger@ n; Table[k = 1; While[f@ k != #, k++] &@ f[2 n - DigitCount[2 n, 2, 1]]; k, {n, 106}] (* or, faster *)
Table[Times @@ MapIndexed[(Prime@ First@ #2)^#1 &, #] &@ If[Length# == 1 && #[[1, 1]] == 1, {0}, Reverse@ Sort@ #[[All, -1]]] &@ FactorInteger[2 n - DigitCount[2 n, 2, 1]], {n, 106}] (* Michael De Vlieger, Nov 21 2016 *)

Prog

(Scheme) (define (A278257 n) (A046523 (A005187 n)))

Crossrefs

Cf A005187, A046523.

Sequence in context: A174147 A163897 A278541 * A278533 A204898 A240295

Adjacent sequences: A278254 A278255 A278256 * A278258 A278259 A278260

Keyword

nonn

Author

Antti Karttunen, Nov 19 2016

Status

approved