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.

Previous Showing 11-13 of 13 results.

A165285 Primes which are the sum of at least 2 consecutive pars "Prime and PreviousNumber".

Original entry on oeis.org

17, 43, 59, 73, 79, 101, 109, 139, 163, 191, 197, 233, 239, 283, 317, 331, 379, 419, 433, 439, 443, 463, 467, 499, 521, 569, 571, 599, 617, 619, 641, 739, 743, 787, 811, 863, 911, 919, 941, 967, 971, 1021, 1039, 1061, 1063, 1087, 1097, 1109, 1117, 1229, 1289
Offset: 1

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Author

Keywords

Comments

(1+2)+(2+3)+(4+5)=17, (4+5)+(6+7)+(10+11)=43, (6+7)+(10+11)+(12+13)=59,..

Crossrefs

Programs

  • Mathematica
    lst={};Do[s=2*Prime[m]-1;Do[p=Prime[n];s+=(2*p-1);If[PrimeQ[s],If[s<=6793,AppendTo[lst,s]]],{n,m+1,3*5!}],{m,1,3*5!}];lst=Take[Union@lst,200]

A326581 Odd integers which are prime or square.

Original entry on oeis.org

1, 3, 5, 7, 9, 11, 13, 17, 19, 23, 25, 29, 31, 37, 41, 43, 47, 49, 53, 59, 61, 67, 71, 73, 79, 81, 83, 89, 97, 101, 103, 107, 109, 113, 121, 127, 131, 137, 139, 149, 151, 157, 163, 167, 169, 173, 179, 181, 191, 193, 197, 199, 211, 223, 225, 227, 229, 233, 239, 241
Offset: 1

Views

Author

Peter Luschny, Jul 15 2019

Keywords

Comments

Contains for example 729=27^2 and hence differs from A062090. - R. J. Mathar, Jul 08 2025

Crossrefs

Programs

  • Maple
    s := n -> if irem(n, 2) = 1 and (isprime(n) or issqr(n)) then n else NULL fi:
    seq(s(n), n=0..241);
  • Mathematica
    Select[Range[1, 241, 2], Or[IntegerQ@ Sqrt@ #, PrimeQ@ #] &] (* Michael De Vlieger, Jul 15 2019 *)

Formula

Union of A065091 and A016754.

A155187 Prime numbers q of primitive Pythagorean triangles such that perimeters are averages of twin prime pairs, p+1=q(prime), a=q^2-p^2, c=q^2+p^2, b=2*p*q, ar=a*b/2; s=a+b+c, s-+1 are primes.

Original entry on oeis.org

2, 3, 11, 71, 227, 491, 683, 1103, 1187, 2591, 3923, 4271, 4931, 6737, 7193, 7703, 8093, 8753, 8963, 9173, 9377, 10271, 13043, 13451, 13997, 15233, 15443, 15803, 15887, 17957, 18701, 19961, 20681, 21701, 22031, 22073, 24371, 24473, 24683
Offset: 1

Views

Author

Keywords

Comments

p=1, q=2(prime), a=3, b=4, c=5, s=12-+1 primes, ...

Crossrefs

Programs

  • Mathematica
    lst={};Do[p=n;q=p+1;a=q^2-p^2;c=q^2+p^2;b=2*p*q;ar=a*b/2;s=a+b+c;If[PrimeQ[s-1]&&PrimeQ[s+1],If[PrimeQ[q],AppendTo[lst,q]]],{n,8!}];lst
Previous Showing 11-13 of 13 results.