A138873 -id:A138873 - cp's OEIS frontend

A138867 First two digits of n-th even superperfect number A061652(n).

2, 4, 16, 64, 40, 65, 26, 10, 11, 30, 81, 85, 34, 26, 52, 73, 22, 12, 95, 14, 23, 17, 14, 21, 22, 20, 42, 26, 26, 25, 37, 87, 64, 20, 40, 31, 63, 21, 46, 62, 14, 61, 15, 62, 10, 84, 15

Offset: 1

Omar E. Pol, Apr 02 2008

Also, first two digits of n-th superperfect number A019279(n), if there are no odd superperfect numbers.

Cf. A019279, A061652, A138862, A138868, A138869, A138873.

a(12)-a(31) from R. J. Mathar, Feb 05 2010

a(32)-a(47) from Jinyuan Wang, Mar 14 2020

A138876 First 3 digits of n-th even perfect number.

Original entry on oeis.org

6, 28, 496, 812, 335, 858, 137, 230, 265, 191, 131, 144, 235, 141, 541, 108, 994, 335, 182, 407, 114, 598, 395, 931, 100, 811, 365, 144, 136, 131, 278, 151, 838, 849, 331, 194, 811, 955, 427, 793, 448, 746, 497, 775, 204, 144, 500

Offset: 1

Omar E. Pol, Apr 02 2008

As of August 6, 2018, GIMPS reports that all Mersenne primes through the 47th have been positively identified, i.e., that there are no further such primes below the 47th. Thus, the sequence through a(47), i.e., through the term 500, is complete. Additional terms (169, 451, 109) are correct but it is still possible that more terms may be found above a(47) but below a(50). [Harvey P. Dale, Jul 17 2011] [Updated by Ivan Panchenko, Aug 06 2018]

Jan Munch Pedersen, Known Perfect Numbers [From Steven Bi (chenhsi(AT)stanford.edu), Jan 18 2009] [Replaced with Wayback Machine link by _Felix Fröhlich_, Aug 04 2018]
Omar E. Pol, Los numeros perfectos

Cf. A000396, A135617, A138864, A138873, A138877.

First three digits of each term from A138877. [Steven Bi (chenhsi(AT)stanford.edu), Jan 18 2009]

f[n_] := Block[{e, p, mpe = MersennePrimeExponent@ n}, p = (2^mpe - 1) 2^(mpe - 1); e = IntegerLength@ p - 3; If[e < 1, p, Quotient[p, 10^e]]]; Array[f, 44] (* Robert G. Wilson v, Aug 06 2018 *)

a(15)-a(31) added by Steven Bi (chenhsi(AT)stanford.edu), Jan 18 2009
Corrected a(27) and added a(32) through a(40) by Harvey P. Dale, Jul 17 2011
Definition changed (inserting the word "even") and a(41)-a(47) added by Ivan Panchenko, Aug 04 2018

cp's OEIS Frontend

A138867 First two digits of n-th even superperfect number A061652(n).

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