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.

Showing 1-2 of 2 results.

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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Author

Keywords

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

A230953 Boustrophedon transform of odd primes, cf. A065091.

Original entry on oeis.org

3, 8, 20, 53, 154, 505, 1944, 8651, 44046, 252271, 1605874, 11245261, 85907084, 710970323, 6336648426, 60510526207, 616355168958, 6670526004559, 76438597647616, 924584128977111, 11772170758462928, 157382330019694067, 2204239468545788024, 32275035859881159165
Offset: 0

Views

Author

Reinhard Zumkeller, Nov 03 2013

Keywords

Crossrefs

Programs

  • Haskell
    a230953 n = sum $ zipWith (*) (a109449_row n) $ tail a000040_list
    
  • Mathematica
    t[n_, 0] := Prime[n+2]; 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 accumulate, count, islice
    from sympy import prime
    def A230953_gen(): # generator of terms
        blist = tuple()
        for i in count(2):
            yield (blist := tuple(accumulate(reversed(blist),initial=prime(i))))[-1]
    A230953_list = list(islice(A230953_gen(),40)) # Chai Wah Wu, Jun 12 2022

Formula

a(n) = Sum_{k=0..n} A109449(n,k)*A000040(k+2).
E.g.f.: (sec(x) + tan(x)) * Sum_{k>=0} prime(k+2)*x^k/k!. - Ilya Gutkovskiy, Jun 26 2018
Showing 1-2 of 2 results.