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.

A285116 Triangle read by rows: T(0,n) = T(n,n) = 1; and for n > 0, 0 < k < n, T(n,k) = C(n-1,k-1) OR C(n-1,k), where C(n,k) is binomial coefficient (A007318) and OR is bitwise-OR (A003986).

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 3, 3, 1, 1, 3, 3, 3, 1, 1, 5, 6, 6, 5, 1, 1, 5, 15, 10, 15, 5, 1, 1, 7, 15, 31, 31, 15, 7, 1, 1, 7, 23, 55, 35, 55, 23, 7, 1, 1, 9, 28, 60, 126, 126, 60, 28, 9, 1, 1, 9, 45, 116, 126, 126, 126, 116, 45, 9, 1, 1, 11, 47, 125, 250, 254, 254, 250, 125, 47, 11, 1, 1, 11, 63, 183, 495, 462, 462, 462, 495, 183, 63, 11, 1
Offset: 0

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Author

Antti Karttunen, Apr 16 2017

Keywords

Examples

			Rows 0 - 12 of the triangle:
  1,
  1, 1,
  1, 1, 1,
  1, 3, 3, 1,
  1, 3, 3, 3, 1,
  1, 5, 6, 6, 5, 1,
  1, 5, 15, 10, 15, 5, 1,
  1, 7, 15, 31, 31, 15, 7, 1,
  1, 7, 23, 55, 35, 55, 23, 7, 1,
  1, 9, 28, 60, 126, 126, 60, 28, 9, 1,
  1, 9, 45, 116, 126, 126, 126, 116, 45, 9, 1,
  1, 11, 47, 125, 250, 254, 254, 250, 125, 47, 11, 1,
  1, 11, 63, 183, 495, 462, 462, 462, 495, 183, 63, 11, 1
		

Crossrefs

Cf. A285113 (row sums).

Programs

  • Mathematica
    T[n_, k_]:= If[n==0 || n==k, 1, BitOr[Binomial[n - 1, k - 1], Binomial[n - 1, k]]]; Table[T[n, k], {n, 0, 12}, {k, 0, n}] // Flatten (* Indranil Ghosh, Apr 16 2017 *)
  • PARI
    T(n, k) = if (n==0 || n==k, 1, bitor(binomial(n - 1, k - 1), binomial(n - 1, k)));
    for(n=0, 12, for(k=0, n, print1(T(n, k),", ");); print();) \\ Indranil Ghosh, Apr 16 2017
  • Scheme
    (define (A285116 n) (A285116tr (A003056 n) (A002262 n)))
    (define (A285116tr n k) (cond ((zero? k) 1) ((= k n) 1) (else (A003986tr (A007318tr (- n 1) (- k 1)) (A007318tr (- n 1) k))))) ;; Where A003986bi implements bitwise-OR (A003986) and A007318tr gives the binomial coefficients (A007318).
    

Formula

T(0,n) = T(n,n) = 1; and for n > 0, 0 < k < n, T(n,k) = C(n-1,k-1) OR C(n-1,k), where C(n,k) is binomial coefficient (A007318) and OR is bitwise-OR (A003986).
T(n,k) = A285117(n,k) + A285118(n,k).
C(n,k) = T(n,k) + A285118(n,k). [Where C(n,k) = A007318.]