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.

A153801 Index of Mersenne number A000225 that is also Mersenne prime A000668, minus n-th prime: a(n) = A000043(n) - A000040(n).

Original entry on oeis.org

0, 0, 0, 0, 2, 4, 2, 12, 38, 60, 76, 90, 480, 564, 1232, 2150, 2222, 3156, 4186, 4352, 9616, 9862, 11130, 19848, 21604, 23108, 44394, 86136, 110394, 131936, 215964, 756708, 859296, 1257648, 1398120, 2976070, 3021220, 6972430, 13466750, 20995838, 24036404, 25964770
Offset: 1

Views

Author

Omar E. Pol, Jan 13 2009

Keywords

Links

Crossrefs

Cf. A000040, A000043, A000668, A000225, A000396, A007691, A153800, A153802, A153803.

Programs

  • Mathematica
    With[{max = 48}, MersennePrimeExponent[Range[max]] - Prime[Range[max]]] (* Amiram Eldar, Oct 21 2024 *)

Extensions

More terms from R. J. Mathar, Feb 19 2009
More terms from Jinyuan Wang, Mar 02 2020

A153803 a(n) = A153800(n) - A000043(n).

Original entry on oeis.org

0, 0, 0, 0, 0, 2, 6, 10, 49, 103, 122, 167
Offset: 1

Views

Author

Omar E. Pol, Jan 13 2009

Keywords

Crossrefs

Cf. A000040, A000043, A000668, A000225, A000396, A007691, A153800, A153801, A153802.

Programs

  • Mathematica
    a007691[m_] := Block[{f = 0, i = 1}, While[f < m, If[Divisible[DivisorSigma[1, i], i], ++f]; ++i;]; Return[i - 1]]
a153800[n_] := Block[{i = 2, j, f = 0}, While[f < n, j = a007691[i]; If[PerfectNumberQ[j], ++f;]; ++i]; Return[i - 1]]
a[n_] := a153800[n] - MersennePrimeExponent[n]
a /@ Range[1, 4] (* Julien Kluge, Dec 15 2016 *)

A153804 a(n) = A153801(n)/2.

Original entry on oeis.org

0, 0, 0, 0, 1, 2, 1, 6, 19, 30, 38, 45, 240, 282, 616, 1075, 1111, 1578, 2093, 2176, 4808, 4931, 5565, 9924, 10802, 11554, 22197, 43068, 55197, 65968, 107982, 378354, 429648, 628824, 699060, 1488035, 1510610, 3486215, 6733375, 10497919, 12018202, 12982385, 15201133
Offset: 1

Views

Author

Omar E. Pol, Jan 13 2009

Keywords

Links

Crossrefs

Cf. A000040, A000043, A153800, A153801, A153802.

Programs

  • Mathematica
    With[{max = 48}, (MersennePrimeExponent[Range[max]] - Prime[Range[max]]) / 2] (* Amiram Eldar, Oct 21 2024 *)

Formula

a(n) = (A000043(n) - A000040(n))/2.

Extensions

More terms from R. J. Mathar, Mar 14 2009
More terms from Jinyuan Wang, Mar 02 2020
Showing 1-3 of 3 results.

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

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