A114562 The first occurrence of n in A111701.

1, 4, 3, 8, 5, 36, 7, 16, 9, 20, 11, 72, 13, 28, 15, 32, 17, 108, 19, 40, 21, 44, 23, 144, 25, 52, 27, 56, 29, 900, 31, 64, 33, 68, 35, 216, 37, 76, 39, 80, 41, 252, 43, 88, 45, 92, 47, 288, 49, 100, 51, 104, 53, 324, 55, 112, 57, 116, 59, 1800, 61, 124, 63, 128, 65, 396, 67

Offset: 1

Author

Robert G. Wilson v, Feb 04 2006

Keywords

• nonn

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A053589, A111701.

Complement of this sequence A095300.

Programs

Mathematica

f[n_] := Block[{m = n, k = 1}, While[ IntegerQ[ m/Prime@k], m = m/Prime@k; k++ ]; m]; g[n_] := Block[{k = 1}, While[f@k != n, k++ ]; k]; Array[g, 67]

Formula

a(2n-1) = 2n-1; a(2n) = k*4n for some k>0, if 2n == 0 (mod 3) then k = 3, if 2n ==0 (15 mod) k = 3*5, if 2n ==0 (105 mod) k = 3*5*7, if 2n ==0 (1155 mod) k = 3*5*7*11, etc.

a(n) = n*A053589(n). - David A. Corneth, Mar 30 2021