A372009 Indices k such that A124652(k) is prime.
2, 3, 5, 11, 12, 20, 24, 28, 29, 33, 42, 43, 53, 58, 67, 78, 93, 98, 104, 105, 109, 112, 118, 125, 126, 137, 141, 145, 146, 162, 174, 182, 185, 187, 188, 195, 200, 223, 224, 231, 232, 239, 246, 249, 252, 255, 259, 264, 271, 275, 283, 286, 287, 296, 298, 300, 326
Offset: 1
Keywords
Examples
Let b(x) = A124652(x). Table of first terms. n a(n) b(a(n)) ----------------- 1 2 2 2 3 3 3 5 5 4 11 11 5 12 7 6 20 31 7 24 13 8 28 19 9 29 17 10 33 37 11 42 29 12 43 41 ...
Links
- Michael De Vlieger, Table of n, a(n) for n = 1..2500
- Michael De Vlieger, Log log scatterplot of A124652(n), n = 1..25000, showing primes in red.
Programs
-
Mathematica
nn = 300; c[_] := False; rad[x_] := rad[x] = Times @@ FactorInteger[x][[All, 1]]; f[x_] := Select[Range[x], Divisible[x, rad[#]] &]; Array[Set[{a[#], c[#]}, {#, True}] &, 2]; s = a[1] + a[2]; {2}~Join~Reap[Do[r = f[s]; k = SelectFirst[r, ! c[#] &]; If[PrimeQ[k], Sow[i]]; c[k] = True; s += k, {i, 3, nn}] ][[-1, 1]]
Formula
Proper subset of A372028.
Comments