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

1,1

Comments

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

Links

Table of n, a(n) for n=1..48.

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

Example

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

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 *)

Crossrefs

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

Sequence in context: A020831 A298777 A156590 * A019930 A169843 A329591

Adjacent sequences: A135614 A135615 A135616 * A135618 A135619 A135620

Keyword

nonn,base,more

Author

Omar E. Pol, Mar 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

Status

approved