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.

A359640 a(n) is the least odd prime not in A001359 such that all subsequent composites in the gap up to the next prime have exactly n odd prime factors, counted with multiplicity.

Original entry on oeis.org

307, 1999, 101527, 7146697, 272572999, 4809363523
Offset: 2

Views

Author

Hugo Pfoertner, Jan 16 2023

Keywords

Examples

			a(2) = 307: 308 = 2^2*7*11, 309 = 3*103, 310 = 2*5*31, all have exactly 2 odd prime factors.
		

Crossrefs

Programs

  • PARI
    a087436(n) = bigomega (n >> valuation (n, 2));
    a359640(maxp) = {my(k=2, pp=5); forprime (p=7, maxp, my(mi=oo, ma=0); if (p-pp>2, for (j=pp+1, p-1, my(mo=a087436(j)); if (mo
    				

A359639 a(n) is the least odd prime not in A001359 such that all subsequent composites in the gap up to the next prime have at least n odd prime factors, counted with multiplicity.

Original entry on oeis.org

97, 1999, 101527, 6666547, 272572999, 3819770107, 410274361249
Offset: 2

Views

Author

Hugo Pfoertner, Jan 16 2023

Keywords

Examples

			a(2) = 97: 98 = 2*7^2, 99 = 3^2*11, 100 = 2^2*5^2 have 2 or 3 odd prime factors, so the minimum 2 is achieved.
a(3) = 1999: 2000 has the 3 odd prime factors 5^3, 2001 = 3*23*29, 2002 = 2*7*11*13.
		

Crossrefs

Programs

  • PARI
    a087436(n) = bigomega (n >> valuation (n, 2));
    a359639(maxp) = {my(k=2,pp=5); forprime (p=7, maxp, my(mi=oo); if (p-pp>2, for (j=pp+1, p-1, my(mo=a087436(j)); if (mo=k, print1(pp,", "); k++)); pp=p)};
    a359639(3*10^8)

A359638 a(n) is the least odd prime not in A001359 such that all subsequent composites in the gap up to the next prime have exactly n prime factors, counted with multiplicity.

Original entry on oeis.org

601, 1429, 81547, 248749, 27140749, 310314157, 3566181247
Offset: 3

Views

Author

Hugo Pfoertner, Jan 16 2023

Keywords

Crossrefs

Programs

  • PARI
    a359638(maxp) = {my (k=3, pp=3); forprime (p=5, maxp, my (mi=oo, ma=0); if (p-pp>2, for (j=pp+1, p-1, my(mo=bigomega(j)); if(mo
    				
Showing 1-3 of 3 results.