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 1-2 of 2 results.

A154587 Numbers that can be expressed both as the sum of first prime numbers and as the sum of first nonprime numbers.

Original entry on oeis.org

0, 5, 28, 71208, 74139, 9260197734, 12374540078, 7574780746329, 11101148723618, 102581905748236, 3325997869054417, 2886018916559052244845, 46437379006448216748610, 120197329614203475099994
Offset: 1

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Author

Keywords

Comments

Is this sequence finite?
Intersection of A007504 and A053767 generates A294174. - R. J. Mathar, Jan 17 2009
Heuristically, the sequence is infinite with about 2 sqrt(log x) members up to x. - Charles R Greathouse IV, Aug 14 2013

Examples

			5 = 2+3 = 1+4. 28 = 2+3+5+7+11 = 1+4+6+8+9.
		

Crossrefs

Intersection of A007504 and A051349. - R. J. Mathar, Jan 17 2009

Programs

  • Maple
    P:=proc(q) local a,b,c,d,n; a:=0; b:=0; c:=0; d:=0; print(a);
    for n from 1 to q do b:=nextprime(b); a:=a+b;
    while cPaolo P. Lava, Feb 23 2018
  • Mathematica
    With[{p = Prime@ Range[10^7]}, {0}~Join~Intersection[Accumulate@ p, Accumulate@ Complement[Range@ Max@ p, p]]] (* Michael De Vlieger, Feb 25 2018 *)

Extensions

Corrected definition and a(6)-a(7) from R. J. Mathar, Jan 17 2009
a(8)-a(11) from Donovan Johnson, Feb 19 2009
a(12)-a(14) from Giovanni Resta, Aug 14 2013
Edited and a(1)=0 prepended by Max Alekseyev, Feb 10 2018

A154588 Numbers that can be expressed as the sum of the first j integer numbers or the first k nonprime numbers, with j and k >=1.

Original entry on oeis.org

1, 28, 435, 10296, 415416, 1062153, 3703281, 426626655, 782002378, 102886232631, 1636197988776, 2749764593278, 61972139524851, 813577626225078, 1604393353172781, 3603538956517305, 44000970048906445, 83556903098276790, 208955344344897381
Offset: 1

Views

Author

Paolo P. Lava & Giorgio Balzarotti, Jan 16 2009, Jan 19 2009

Keywords

Comments

The indices (j,k) where A000217(j) = A051349(k) are (1,1), (7,5), (29,23), (143,123), (911,823), (1457,1327), (2721,2501), (29210,27488), (39547,37295) , (453621,433381) , (1808976,1737137) , (2345107,2253859) , (11133026,10746793), (40338012,39053670), (56646153,54880858) , (84894510,82314170) , (296651209,288273745), (408795555,397457085), (646460121,628975505). - Donovan Johnson, Sep 11 2009

Examples

			28 = A000217(7) = A051349(5).
435 = A000217(19) = A051349(23).
10296 = A000217(143) = A051349(123).
		

Crossrefs

Programs

  • Mathematica
    Module[{nn=10^7,np},np=Select[Range[nn],!PrimeQ[#]&];Intersection[Accumulate[Range[ nn]],Accumulate[ np]]] (* The program generates the first 12 terms of the sequence. *) (* Harvey P. Dale, Feb 08 2024 *)

Formula

(A000217 INTERSECT A051349) MINUS {0}. - R. J. Mathar, Jan 21 2009

Extensions

10256 replaced with 10296 and two more terms added by R. J. Mathar, Jan 21 2009
Extended beyond a(9) by Donovan Johnson, Sep 11 2009
Showing 1-2 of 2 results.