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.

A058848 Numbers k such that the sum of the first k odd composites is palindromic.

Original entry on oeis.org

1, 12, 25, 61, 108, 211, 1344, 2339, 10539, 78409, 283181, 1748747, 1795423, 2386702, 2819089, 179101605, 1923088106, 2822581688, 7794689270, 17381011919, 25635268093, 28780043265, 97973526253
Offset: 1

Views

Author

Patrick De Geest, Dec 15 2000

Keywords

Comments

Sequence of odd composite numbers is 9 + 15 + 21 + 25 + 27 + 33 + ... + z. For values of z see A058849.

Links

Crossrefs

Cf. A058849, A058850, A262044.

Programs

Extensions

a(20) from Donovan Johnson, Sep 01 2012
a(21)-a(23) from Chai Wah Wu, Dec 06 2019
Comment clarified by Harvey P. Dale, Aug 05 2025

A262044 Partial sum of the first n odd composite numbers.

Original entry on oeis.org

9, 24, 45, 70, 97, 130, 165, 204, 249, 298, 349, 404, 461, 524, 589, 658, 733, 810, 891, 976, 1063, 1154, 1247, 1342, 1441, 1546, 1657, 1772, 1889, 2008, 2129, 2252, 2377, 2506, 2639, 2774, 2915, 3058, 3203, 3350, 3503, 3658, 3817, 3978, 4143, 4312
Offset: 1

Views

Author

R. J. Mathar, Sep 09 2015

Keywords

Comments

Intersection with A002113 gives A058850.

Links

Crossrefs

Cf. A058850.

Programs

  • Maple
    A262044 := proc(n)
    add(A071904(i),i=1..n) ;
end proc:
  • Mathematica
    Accumulate[Select[Range[9,191,2],CompositeQ]] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Jun 09 2017 *)

Formula

a(n) = Sum_{i=1..n} A071904(i).

A058849 Sum of odd composites up to n is palindromic.

Original entry on oeis.org

9, 55, 99, 215, 357, 663, 3725, 6321, 26999, 191363, 675861, 4073533, 4180943, 5540147, 6531789, 400974175, 4248550291, 6224149881, 17109266357, 38023877981, 55995454633, 62836534343, 212955815417
Offset: 1

Views

Author

Patrick De Geest, Dec 15 2000

Keywords

Comments

Sequence is 9 + 15 + 21 + 25 + 27 + 33 + ... + n.

Links

Crossrefs

Cf. A058848, A058850.

Programs

  • Maple
    nextA071904 := proc(n) local a ; a := n + 2 - ((n+1) mod 2); while isprime(a) do a := a+2 ; od ; RETURN(a) ; end: isA002113 := proc(n) local drev,i ; drev := convert(n,base,10) ; for i from 1 to nops(drev)/2 do if op(i,drev) <> op(-i,drev) then RETURN(false) ; fi ; od ; RETURN(true) ; end: nextA058844 := proc(n,nsum) local a, asum ; a := nextA071904(n) ; asum := nsum+a ; while not isA002113(asum) do a := nextA071904(a) ; asum := asum+a ; od ; RETURN([a, asum]) ; end: n := 9 ; nsum := 9 ; nnsum := [n,nsum] ; for i from 1 to 40 do print(op(1,nnsum)) ; nnsum := nextA058844(op(1,nnsum),op(2,nnsum)) ; od : # R. J. Mathar, Jan 29 2007

Formula

Sum_{i=1..j} A071904(i) = A002113(k) for A071904(j) = n and some k. - R. J. Mathar, Jan 29 2007

Extensions

a(20) from Donovan Johnson, Sep 01 2012
a(21)-a(23) from Chai Wah Wu, Dec 06 2019
Showing 1-3 of 3 results.

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

Content is available under The OEIS End-User License Agreement.