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.

A346043 a(n) is the position of A138534(n) in A025487.

Original entry on oeis.org

1, 2, 6, 17, 67, 166, 676, 1373, 4475, 10446, 30036, 51032, 196386, 315302, 737515, 1654229, 4227565, 6301902, 17975187, 26010425, 70085244, 133337963
Offset: 0

Views

Author

Amiram Eldar, Jul 02 2021

Keywords

Examples

			A138534(2) = A025487(6) = 12, so a(2) = 6.

Crossrefs

Cf. A025487, A138534.
Similar sequences: A098718, A098719, A293635, A306802.

Programs

  • Mathematica
    lps = Cases[Import["https://oeis.org/A025487/b025487.txt", "Table"], {, }][[;; , 2]]; s = {}; Do[p = Position[lps, Product[Prime[k]^Floor[n/k], {k, 1, n}]]; If[p == {}, Break[]]; AppendTo[s, p[[1, 1]]], {n, 0, 20}]; s
  • PARI
    f(m) = my(c=1, p, q=2, v=vector(logint(m, 2), i, 2^i), w); while(#v, c+=#v; p=q; q=nextprime(q+1); w=List([]); for(i=1, #v, for(j=1, min(valuation(v[i], p), logint(m\v[i], q)), listput(w, v[i]*q^j))); v=w); c;
a(n) = f(prod(k=1, n, prime(k)^(n\k))); \\ Jinyuan Wang, Jul 08 2021

Formula

A025487(a(n)) = A138534(n).

Extensions

a(20)-a(21) from Jinyuan Wang, Jul 08 2021

A346407 a(n) is the position of A051451(n) in A025487.

Original entry on oeis.org

1, 2, 4, 6, 13, 29, 36, 55, 112, 223, 264, 514, 956, 1749, 2345, 2847, 5005, 8567, 9507, 16073, 26792, 43730, 70482, 88969, 140871, 221370, 342958, 368588, 565510, 859401, 1290994, 1927925, 2128165, 3142980, 4616207, 6754033, 9810997, 14133201, 20230329, 28744301
Offset: 1

Views

Author

Amiram Eldar, Jul 15 2021

Keywords

Comments

Equivalently, the positions of the distinct terms of A003418 in A025487.

Examples

			A138534(1) = A025487(1) = 1, so a(1) = 1.
A138534(2) = A025487(2) = 2, so a(2) = 2.
A138534(3) = A025487(4) = 6, so a(3) = 4.

Crossrefs

Cf. A003418, A051451, A025487.
Similar sequences: A098718, A098719, A293635, A306802, A346043.

Programs

  • Mathematica
    lps = Cases[Import["https://oeis.org/A025487/b025487.txt", "Table"], {, }][[;; , 2]]; s = {}; lcms = Union @ Table[LCM @@ Range[n], {n, 1, 31}]; Do[p = Position[lps, lcms[[n]]]; If[p == {}, Break[]]; AppendTo[s, p[[1, 1]]], {n, 1, Length[lcms]}]; s

Formula

A025487(a(n)) = A003418(n).

A363456 Positions of the terms of the Chernoff sequence (A006939) in A025487.

Original entry on oeis.org

1, 2, 6, 27, 150, 900, 5697, 37226, 246280, 1648592, 11204274
Offset: 0

Views

Author

Amiram Eldar, Jun 03 2023

Keywords

Comments

Indices of records in A363455.

Examples

			A006939(0) = A025487(1) = 1, so a(0) = 1.
A006939(1) = A025487(2) = 2, so a(1) = 2.
A006939(2) = A025487(6) = 12, so a(2) = 6.

Crossrefs

Cf. A006939, A025487, A363455.
Similar sequences: A098718, A098719, A293635, A306802, A346043, A346407.

Programs

  • Mathematica
    lps = Cases[Import["https://oeis.org/A025487/b025487.txt", "Table"], {, }][[;; , 2]];
cher = Table[Product[Prime[k]^(n - k + 1), {k, 1, n}], {n, 0, 8}]
Position[lps, #] & /@ cher // Flatten

Formula

A025487(a(n)) = A006939(n).
A363455(a(n)) = n.
Showing 1-3 of 3 results.

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

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