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.

A275804 Numbers with at most one nonzero digit on each digit slope of the factorial base representation of n.

Original entry on oeis.org

0, 1, 2, 3, 4, 6, 7, 8, 9, 10, 12, 13, 16, 18, 20, 24, 25, 26, 27, 28, 30, 31, 32, 33, 34, 36, 37, 40, 42, 44, 48, 49, 50, 51, 52, 60, 61, 64, 66, 68, 72, 73, 76, 78, 79, 82, 90, 96, 98, 102, 104, 108, 120, 121, 122, 123, 124, 126, 127, 128, 129, 130, 132, 133, 136, 138, 140, 144, 145, 146, 147, 148, 150, 151, 152, 153, 154, 156, 157, 160
Offset: 0

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Author

Antti Karttunen, Aug 10 2016

Keywords

Comments

Indexing starts from zero, because a(0) = 0 is a special case in this sequence.
Numbers n for which A275947(n) = 0 or equally, for which A275811(n) <= 1.
Numbers n for which A008683(A275734(n)) <> 0, that is, indices of squarefree terms in A275734.
Numbers n for which A060130(n) = A060502(n).
Numbers with at most one nonzero digit on each digit slope of the factorial base representation of n (see A275811 and A060502 for the definition of slopes in this context). More exactly: numbers n in whose factorial base representation (A007623) there does not exist a pair of digit positions i_1 and i_2 with nonzero digits d_1 and d_2, such that (i_1 - d_1) = (i_2 - d_2).

Crossrefs

Complement: A275805.
Indices of zeros in A275947 and A275962.
Intersection with A276005 gives A261220.
Cf. A059590 (a subsequence).

Programs

  • Python
    from operator import mul
    from sympy import prime, factorial as f
    from sympy.ntheory.factor_ import core
    def a007623(n, p=2): return n if n

    0 else '0' for i in x)[::-1] return 0 if n==1 else sum([int(y[i])*f(i + 1) for i in range(len(y))]) def a(n): return 1 if n==0 else a275732(n)*a(a257684(n)) def ok(n): return 1 if n==0 else core(a(n))==a(n) print([n for n in range(201) if ok(n)]) # Indranil Ghosh, Jun 19 2017