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.

A283985 Sums of distinct terms of A143293: a(n) = Sum_{k>=0} A030308(n,k)*A143293(k).

Original entry on oeis.org

0, 1, 3, 4, 9, 10, 12, 13, 39, 40, 42, 43, 48, 49, 51, 52, 249, 250, 252, 253, 258, 259, 261, 262, 288, 289, 291, 292, 297, 298, 300, 301, 2559, 2560, 2562, 2563, 2568, 2569, 2571, 2572, 2598, 2599, 2601, 2602, 2607, 2608, 2610, 2611, 2808, 2809, 2811, 2812, 2817, 2818, 2820, 2821, 2847, 2848, 2850, 2851, 2856, 2857, 2859, 2860, 32589
Offset: 0

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Author

Antti Karttunen, Mar 19 2017

Keywords

Comments

Indexing starts from zero, with a(0) = 0.

Crossrefs

Programs

  • PARI
    A143293(n) = { if(n==0, return(1)); my(P=1, s=1); forprime(p=2, prime(n), s+=P*=p); s; }; \\ This function from Charles R Greathouse IV, Feb 05 2014
    A030308(n,k) = bittest(n,k);
    A283985(n) = sum(i=0,(#binary(n)-1),A030308(n,i)*A143293(i));
    
  • Python
    from sympy import primorial, primepi, prime, primerange, factorint
    from operator import mul
    from functools import reduce
    def a002110(n): return 1 if n<1 else primorial(n)
    def a276085(n):
        f=factorint(n)
        return sum([f[i]*a002110(primepi(i) - 1) for i in f])
    def P(n): return reduce(mul, [i for i in primerange(2, n + 1)])
    def a108951(n):
        f = factorint(n)
        return 1 if n==1 else reduce(mul, [P(i)**f[i] for i in f])
    def a019565(n): return reduce(mul, (prime(i+1) for i, v in enumerate(bin(n)[:1:-1]) if v == '1')) if n > 0 else 1 # after Chai Wah Wu
    def a(n): return a276085(a108951(a019565(n)))
    print([a(n) for n in range(101)]) # Indranil Ghosh, Jun 22 2017
  • Scheme
    (define (A283985 n) (A276085 (A283477 n)))
    

Formula

a(n) = Sum_{k>=0} A030308(n,k)*A143293(k).
a(n) = A276085(A283477(n)).
Other identities. For all n >= 0:
a(2^n) = A143293(n).