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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A382835 Array read by ascending antidiagonals: A(n,k) = (6*n + 1)*(12*n + 1)*Product_{i=0..k-2} (9*2^i*n + 1) with k >= 2.

Original entry on oeis.org

1, 91, 1, 325, 1729, 1, 703, 12025, 63973, 1, 1225, 38665, 877825, 4670029, 1, 1891, 89425, 4214485, 127284625, 677154205, 1, 2701, 172081, 12966625, 914543245, 36785256625, 195697565245, 1, 3655, 294409, 31146661, 3747354625, 395997225085, 21225093072625, 112917495146365, 1
Offset: 0

Views

Author

Stefano Spezia, Apr 06 2025

Keywords

Comments

A(n,k) is a Carmichael number with k prime factors if n is such all k factors are prime numbers and 2*k-4 divides n (see Ribenboim).

Examples

			The array begins as:
     1,      1,        1,           1,              1, ...
    91,   1729,    63973,     4670029,      677154205, ...
   325,  12025,   877825,   127284625,    36785256625, ...
   703,  38665,  4214485,   914543245,   395997225085, ...
  1225,  89425, 12966625,  3747354625,  2162223618625, ...
  1891, 172081, 31146661, 11243944621,  8106884071741, ...
  2701, 294409, 63886753, 27662964049, 23928463902385, ...
  ...
		

References

  • Paulo Ribenboim, The Little Book of Bigger Primes, Springer-Verlag NY 2004. See p. 101.

Crossrefs

Cf. A000012 (n=0), A002997, A318646, A382809 (k=3), A382836 (antidiagonal sums).

Programs

  • Mathematica
    A[n_,k_]:=(6n+1)(12n+1)Product[9*2^i*n+1,{i,k-2}];Table[A[n-k,k],{n,0,9},{k,2,n}]//Flatten
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