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.

A000747 Boustrophedon transform of primes.

Original entry on oeis.org

2, 5, 13, 35, 103, 345, 1325, 5911, 30067, 172237, 1096319, 7677155, 58648421, 485377457, 4326008691, 41310343279, 420783672791, 4553946567241, 52184383350787, 631210595896453, 8036822912123765, 107444407853010597, 1504827158220643895, 22034062627659931905
Offset: 0

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Crossrefs

Programs

  • Haskell
    a000747 n = sum $ zipWith (*) (a109449_row n) a000040_list
    -- Reinhard Zumkeller, Nov 03 2013
    
  • Mathematica
    t[n_, 0] := Prime[n+1]; t[n_, k_] := t[n, k] = t[n, k-1] + t[n-1, n-k]; a[n_] := t[n, n]; Array[a, 30, 0] (* Jean-François Alcover, Feb 12 2016 *)
  • Python
    from itertools import islice, count, accumulate
    from sympy import prime
    def A000747_gen(): # generator of terms
        blist = tuple()
        for i in count(1):
            yield (blist := tuple(accumulate(reversed(blist),initial=prime(i))))[-1]
    A000747_list = list(islice(A000747_gen(),30)) # Chai Wah Wu, Jun 11 2022

Formula

a(n) = Sum_{k=0..n} A109449(n,k)*A000040(k+1). - Reinhard Zumkeller, Nov 03 2013
E.g.f.: (sec(x) + tan(x)) * Sum_{k>=0} prime(k+1)*x^k/k!. - Ilya Gutkovskiy, Jun 26 2018