cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Showing 1-3 of 3 results.

A138875 Concatenation of first two digits and last two digits of n-th even perfect number.

Original entry on oeis.org

66, 2828, 4996, 8128, 3336, 8556, 1328, 2328, 2676, 1916, 1328, 1428, 2376, 1428, 5428, 1028, 9976, 3356, 1836, 4028, 1116, 5976, 3936, 9356, 1076, 8116, 3656, 1428, 1328, 1316, 2728, 1528, 8336, 8428, 3316, 1976, 8156, 9536, 4256, 7928, 4428, 7428, 4956, 7756, 2028, 1476, 5016
Offset: 1

Views

Author

Omar E. Pol, Apr 02 2008

Keywords

Links

Crossrefs

Cf. A000396, A104511, A138843, A138863, A138866, A138877.

Extensions

More terms from http://amicable.homepage.dk/perfect.htm sent by Steven Bi (chenhsi(AT)stanford.edu), Dec 22 2008
More terms from same site sent by Steven Bi (chenhsi(AT)stanford.edu), Jan 09 2009
More terms from Jinyuan Wang, Mar 14 2020

A138872 Concatenation of first 3 digits and last 3 digits of n-th even superperfect number A061652(n).

Original entry on oeis.org

22, 44, 1616, 6464, 409096, 655536, 262144, 107824, 115976, 309056, 811064, 850864, 343576, 265064, 520544, 737504, 223176, 129536, 953496, 142304, 239056, 173776, 140096, 215736, 224376, 201256, 427336, 268104, 260504, 256656, 373224, 870944
Offset: 1

Views

Author

Omar E. Pol, Apr 02 2008

Keywords

Comments

Also, concatenation of first 3 digits and last 3 digits of n-th superperfect number A019279(n), if there are no odd superperfect numbers.

Crossrefs

Cf. A019279, A061652, A138866, A138877, A138870, A138871.

Extensions

More terms from Max Alekseyev, Feb 11 2012

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

Views

Author

Omar E. Pol, Apr 02 2008

Keywords

Comments

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]

Links

Crossrefs

Cf. A000396, A135617, A138864, A138873, A138877.
First three digits of each term from A138877. [Steven Bi (chenhsi(AT)stanford.edu), Jan 18 2009]

Programs

  • Mathematica
    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 *)

Extensions

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
Showing 1-3 of 3 results.

Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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