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.

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A360529 a(n) is the smallest k > A024619(n) such that rad(k) = rad(A024619(n)), where rad(n) = A007947(n).

Original entry on oeis.org

12, 20, 18, 28, 45, 24, 40, 63, 44, 36, 52, 56, 60, 99, 68, 175, 48, 76, 117, 50, 84, 88, 75, 92, 54, 80, 153, 104, 72, 275, 98, 171, 116, 90, 124, 147, 325, 132, 136, 207, 140, 96, 148, 135, 152, 539, 156, 100, 164, 126, 425, 172, 261, 176, 120, 637, 184, 279, 188, 475, 108, 112, 297, 160, 204, 208
Offset: 1

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Author

Michael De Vlieger, May 01 2023

Keywords

Comments

Permutation of A126706.
Let m = A024619(n) and let R_m be the sequence of numbers k such that rad(k) = rad(m). a(n) gives the successor to m in R_m.

Examples

			A024619(1) = 6; the smallest k > 6 such that rad(k) = 6 is a(1) = 12.
A024619(2) = 10; the smallest k > 10 such that rad(k) = 10 is a(2) = 20.
A024619(3) = 12; the smallest k > 12 such that rad(k) = rad(12) = 6 is a(3) = 18.
		

Crossrefs

Programs

  • Mathematica
    rad[x_] := rad[x] = Times@ FactorInteger[x][[All, 1]]; Table[k = m + 1; Function[r, If[SquareFreeQ[m], m*FactorInteger[m][[1, 1]],  While[rad[k] != r, k++]; k]][rad[m]], {m, Select[Range[2, 104], ! PrimePowerQ[#] &]}]

Formula

a(n) = A065642 \ A001597.
Squarefree m implies a(n) = lpf(m)*m = A020639(m)*m.
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