A138124 Initial digit of n-th even superperfect number A061652(n).

2, 4, 1, 6, 4, 6, 2, 1, 1, 3, 8, 8, 3, 2, 5, 7, 2, 1, 9, 1, 2, 1, 1, 2, 2, 2, 4, 2, 2, 2, 3, 8, 6, 2, 4, 3, 6, 2, 4

Offset: 1

Author

Omar E. Pol and Robert G. Wilson v, Apr 01 2008

Keywords

• base
• nonn

Comments

Also, initial digit of n-th superperfect number A019279(n), if there are no odd superperfect numbers.

Examples

			a(5)=4 because the 5th even superperfect number A061652(5) is 4096 and the initial digit of 4096 is 4.
		

Crossrefs

Cf. A000030, A077648, A019279, A061652, A135613, A135617, A138125.

Programs

Mathematica

lst = {2, 3, 5, 7, 13, 17, 19, 31, 61, 89, 107, 127, 521, 607, 1279, 2203, 2281, 3217, 4253, 4423, 9689, 9941, 11213, 19937, 21701, 23209, 44497, 86243, 110503, 132049, 216091, 756839, 859433, 1257787, 1398269, 2976221, 3021377, 6972593, 13466917}; f[n_] := Block[{pn = 2^(n - 1)}, Quotient[pn, 10^Floor[Log[10, pn]]]]; f@# & /@ (* Robert G. Wilson v, Apr 01 2008 *)

Extensions

a(13)-a(39) from Robert G. Wilson v, Apr 01 2008