A102046 Smallest positive integer greater than a(n - 1) consistent with the condition that n is a member of the sequence if and only if a(n) is congruent to (n!)!.

1, 1, 2, 6, 7, 8, 720, 721, 722, 723, 724, 726, 727, 728, 729, 780, 781, 782, 783, 784, 785, 786, 787, 789, 790, 791, 792, 793, 794, 795, 796, 797, 798, 799, 780, 781, 782, 783, 784, 785, 786, 787, 788, 789, 790, 791, 792, 793, 794, 795, 796, 797, 798, 799

Offset: 0

Author

Michael Joseph Halm, Feb 12 2005

Keywords

• easy
• nonn
• obsc

Comments

The sequence is related to the fake even and fake odd sequences and also the factorial and double factorial sequences, so seems in the short run linear but in the long run exponential.

Examples

			a(6) = 720 because (3!)! = 6! = 720
		

Crossrefs

Cf. A080591, A080588, A000197, A000142.

Formula

a(a(n)) = (n!)!

Extensions

The definition does not match the data. How was this sequence generated? - N. J. A. Sloane, Feb 21 2021