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.

A289661 a(n) is the smallest m such that p = n-th popular prime = A385503(n) is popular on the interval [2,m].

Original entry on oeis.org

2, 3, 45, 70, 1456, 4845, 20332, 46345, 106812, 153032, 592760, 2484190, 2620033, 2623860, 41163150, 237321819, 1966462280, 13690728506, 64322151699, 79838726306, 220355977754, 232268764689, 618745965579, 1882062393429, 9607711921430, 19364051434020, 26393150922356, 37636607775855, 114514665136326, 173974642506024, 228013323182523, 259772852488365, 284600479332862, 644741545074402
Offset: 1

Views

Author

N. J. A. Sloane, Jul 25 2017

Keywords

Comments

See A385503 for further links and information.

Links

Crossrefs

Cf. A006530, A385503, A289662-A289665.

Extensions

Edited, with terms updated from revised version of McNew, by Peter Munn, Jul 04 2025

A385653 Least k such that A385652(k) = n.

Original entry on oeis.org

2, 4, 8, 12, 18, 24, 27, 36, 48, 54, 72, 80, 90, 100, 120, 125, 135, 150, 160, 180, 196, 210, 224, 245, 252, 280, 294, 315, 336, 343, 350, 378, 392, 420, 441, 448, 490, 504, 525, 560, 567, 588, 630, 672, 686, 700, 735, 756, 784, 840, 875, 882, 896, 945, 980
Offset: 1

Views

Author

Pontus von Brömssen, Jul 06 2025

Keywords

Comments

A385654(n) is uniquely popular on the interval [2,a(n)]; see A289662.
Equivalently, a(n) is the least k >= 2 such that A078899(k) = n.

Links

Crossrefs

Cf. A006530, A078899, A289662, A385503, A385652, A385654.

Programs

  • PARI
    gpf(n) = if (n==1,1, vecmax(factor(n)[,1])); \\ A006530
f(n) = my(v=vector(n, k, gpf(k)), s=Set(v)); vecmax(apply(x->#x, vector(#s, i, select(x->(x==s[i]), v)))); \\ A385652
a(n) = my(k=2); while (f(k) !=n, k++); k; \\ Michel Marcus, Jul 06 2025

A385654 Greatest prime factor of A385653(n).

Original entry on oeis.org

2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3, 5, 5, 5, 5, 5, 5, 5, 5, 5, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 13, 13, 13, 13, 13, 7, 13, 13, 13, 13, 13, 13
Offset: 1

Views

Author

Pontus von Brömssen, Jul 06 2025

Keywords

Comments

A number appears in this sequence if and only if it is a uniquely popular prime; see A289662. a(n) is uniquely popular on the interval [2,A385653(n)].

Links

Crossrefs

Cf. A006530, A289662, A385503, A385652, A385653.

Programs

  • PARI
    gpf(n) = if (n==1,1, vecmax(factor(n)[,1])); \\ A006530
f(n) = my(v=vector(n, k, gpf(k)), s=Set(v)); vecmax(apply(x->#x, vector(#s, i, select(x->(x==s[i]), v)))); \\ A385652
a(n) = my(k=2); while (f(k) !=n, k++); gpf(k); \\ Michel Marcus, Jul 06 2025
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.