A054792 Earliest sequence with a(a(n)) = n^3.

0, 1, 3, 8, 5, 64, 7, 216, 27, 10, 729, 12, 1331, 14, 2197, 16, 3375, 18, 4913, 20, 6859, 22, 9261, 24, 12167, 26, 15625, 512, 29, 21952, 31, 27000, 33, 32768, 35, 39304, 37, 46656, 39, 54872, 41, 64000, 43, 74088, 45, 85184, 47, 97336, 49, 110592, 51

Offset

0,3

Links

T. D. Noe, Table of n, a(n) for n = 0..1000

Index entries for sequences of the a(a(n)) = 2n family

Formula

If n is a cube then a(n) = a(n^(1/3))^3, otherwise if the difference between n and the highest cube less than n is odd then a(n) = n+1, otherwise a(n) = (n-1)^3.

Mathematica

a[n_] := a[n] = Which[r = n^(1/3); IntegerQ[r], a[r]^3, OddQ[n - Floor[r]^3], n+1, True, (n-1)^3]; a[0]=0; a[1]=1; Table[a[n], {n, 0, 50}] (* Jean-François Alcover, Aug 07 2012, after formula *)

Crossrefs

Sequence in context: A086872 A363421 A323760 * A144872 A090347 A374922

Adjacent sequences: A054789 A054790 A054791 * A054793 A054794 A054795

Keyword

nice,nonn

Author

Henry Bottomley, Apr 27 2000

Status

approved