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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A218566 Triangle T[r,c]=(r-1)*binomial(r-1,c-1)*(c-1)!*A093883(c), read by rows.

Original entry on oeis.org

0, 1, 3, 2, 12, 240, 3, 27, 1080, 226800, 4, 48, 2880, 1209600, 3657830400, 5, 75, 6000, 3780000, 22861440000, 1267438233600000, 6, 108, 10800, 9072000, 82301184000, 9125555281920000, 11274806061917798400000
Offset: 1

Views

Author

M. F. Hasler, Nov 02 2012

Keywords

Comments

T[b,d] gives the number of positive numbers that can be written in base b with d(d+1)/2 digits such that for each k=1,...,d some digit appears exactly k times, cf. A218560, A167819, A218556 and related sequences.

Examples

			The first 6 rows of the triangle are:
r=1: 0;
r=2: 1, 3;
r=3: 2, 12,  240;
r=4: 3, 27,  1080,  226800;
r=5: 4, 48,  2880,  1209600,  3657830400;
r=6: 5, 75,  6000,  3780000,  22861440000,  1267438233600000.
Row 2 counts the numbers 1 and 4=100[2], 5=101[2], 6=110[2].
Row 3 counts the numbers {1, 2} and {9=100[3], 10=101[3], 12=110[3], 14=112[3], 16=121[3], ..., 25=221[3]} and {248=100012[3], ..., 714=222110[3]}.
		

Programs

  • PARI
    T(r,c)=(r-1)*binomial(r-1,c-1)*(c-1)!*A093883(c)

Formula

T[r,1] = r-1. T[r,2] = 3(r-1)^2. T[r,3] = 60(r-2)(r-1)^2, etc.
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