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 1-5 of 5 results.

A138863 Concatenation of first two digits and last two digits of n-th Mersenne prime A000668(n).

Original entry on oeis.org

33, 77, 3131, 1227, 8191, 1371, 5287, 2147, 2351, 6111, 1627, 1727, 6851, 5327, 1087, 1407, 4451, 2571, 1991, 2807, 4711, 3451, 2891, 4371, 4451, 4011, 8571, 5307, 5207, 5111, 7447, 1787, 1291, 4127, 8111, 6251, 1271, 4391, 9271, 1247, 2907, 1247, 3171, 1271, 2027, 1651, 3111
Offset: 1

Views

Author

Omar E. Pol, Apr 02 2008

Keywords

Links

Crossrefs

Cf. A000668, A080173, A104511, A138816, A138817, A138840, A138841, A138862, A138864, A138865, A138866.

Extensions

More terms from Jinyuan Wang, Mar 14 2020

A138862 First two (i.e., the two most significant) digits of n-th Mersenne prime A000668(n).

Original entry on oeis.org

3, 7, 31, 12, 81, 13, 52, 21, 23, 61, 16, 17, 68, 53, 10, 14, 44, 25, 19, 28, 47, 34, 28, 43, 44, 40, 85, 53, 52, 51, 74, 17, 12, 41, 81, 62, 12, 43, 92, 12, 29, 12, 31, 12, 20, 16, 31
Offset: 1

Views

Author

Omar E. Pol, Apr 02 2008

Keywords

Links

Crossrefs

Cf. A000668, A080173, A138863, A138864, A138865, A138866.

Programs

  • Mathematica
    Join[{3,7},FromDigits[Take[IntegerDigits[#],2]]&/@ (2^MersennePrimeExponent[ Range[ 3,47]]-1)] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Aug 01 2020 *)

Extensions

a(40)-a(47) from Ivan Panchenko, Aug 03 2018
Definition clarified by Harvey P. Dale, Aug 01 2020

A138865 Last 3 digits of n-th Mersenne prime A000668(n).

Original entry on oeis.org

3, 7, 31, 127, 191, 71, 287, 647, 951, 111, 127, 727, 151, 127, 87, 7, 351, 71, 991, 607, 111, 551, 191, 471, 751, 511, 671, 207, 7, 311, 447, 887, 591, 527, 711, 151, 271, 791, 71, 47, 407, 247, 871, 871, 927, 751, 511
Offset: 1

Views

Author

Omar E. Pol, Apr 02 2008

Keywords

Links

Crossrefs

Cf. A000668, A080173, A104511, A138862, A138863, A138864, A138866.

Programs

  • Mathematica
    Array[Mod[2^MersennePrimeExponent[#] - 1, 1000] &, 45] (* Michael De Vlieger, Aug 05 2018 *)

Extensions

a(40)-a(47) from Ivan Panchenko, Apr 03 2018

A138870 First 3 digits of n-th even superperfect number A061652(n).

Original entry on oeis.org

2, 4, 16, 64, 409, 655, 262, 107, 115, 309, 811, 850, 343, 265, 520, 737, 223, 129, 953, 142, 239, 173, 140, 215, 224, 201, 427, 268, 260, 256, 373, 870, 647, 206, 407, 311, 637, 218, 462, 629, 149, 610, 157, 622, 101, 849, 158
Offset: 1

Views

Author

Omar E. Pol, Apr 02 2008

Keywords

Comments

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

Crossrefs

Cf. A019279, A061652, A138864, A138867, A138871, A138872, A138876.

Extensions

a(12)-a(31) from R. J. Mathar, Feb 05 2010
a(32)-a(41) from Max Alekseyev, Feb 11 2012
a(42)-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

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 1-5 of 5 results.

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