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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A385348 Minimum number of products of the form P^2-i^2 to be used to obtain the GCD defined in A380472.

Original entry on oeis.org

1, 3, 2, 4, 4, 6, 6, 4, 7, 16, 18, 7, 7, 14, 15, 15, 21, 9, 11, 19, 18, 24, 33, 11, 26, 13, 14, 47, 48, 17, 14, 19, 14, 54, 43, 14, 22, 34, 40, 33, 17, 39, 14, 17, 36, 54, 67, 38, 21, 26, 18, 135, 40, 19, 25, 25, 24, 79, 78, 20, 25, 25, 24, 101, 30, 25, 24, 24, 34, 24
Offset: 1

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Author

Michel Marcus, Jun 26 2025

Keywords

Crossrefs

Cf. A380472.

Programs

  • PARI
    f(n) = (2*n+2)!*(3/4-(-1)^n/4); \\ A380472
    T(n, j) = gcd(vector(j, k, P=prime(k+n+1); prod(i=1, n, P^2-i^2)));
    a(n) = my(x=f(n)); for (j=1, n^2, if (T(n, j) == x, return(j)));
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