A135617 a(n) is the initial digit of n-th even perfect number.

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

Offset: 1

Author

Omar E. Pol, Mar 01 2008

Keywords

• nonn
• base
• more

Comments

a(n) is also the initial digit of n-th perfect number A000396(n) if there are no odd perfect numbers.

Examples

			a(5) = 3 because the 5th even perfect number is 33550336 and the initial digit of 33550336 is 3.
		

Links

• Omar E. Pol, Los números perfectos, (in Spanish).

Crossrefs

Cf. A000030, A000396, A077648, A094540, A133033.

Programs

Mathematica

lst = {* the list of terms in A000043 *}; f[n_] := Block[{pn = (2^n - 1) (2^(n - 1))}, Quotient[pn, 10^Floor[ Log[10, pn]] ]]; f@# & /@ lst (* Robert G. Wilson v, Apr 01 2008 *)

Extensions

More terms from Robert G. Wilson v, Apr 01 2008

Definition clarified by Omar E. Pol, Apr 14 2018

a(40)-a(47) from Ivan Panchenko, Apr 16 2018

a(48) from Amiram Eldar, Oct 16 2024