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.

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A328379 a(n) is the sum of the distinct numbers whose binary digits appear in order but not necessarily as consecutive digits in the binary representation of n.

Original entry on oeis.org

0, 1, 3, 4, 7, 11, 12, 11, 15, 24, 31, 29, 28, 37, 33, 26, 31, 49, 66, 61, 71, 92, 85, 67, 60, 87, 103, 90, 77, 95, 78, 57, 63, 98, 133, 121, 150, 191, 177, 138, 151, 215, 254, 219, 197, 240, 199, 145, 124, 185, 237, 210, 235, 293, 262, 199, 165, 230, 263, 223
Offset: 0

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Author

Rémy Sigrist, Nov 30 2019

Keywords

Examples

			The first terms, alongside the binary representations of n as well as those of the numbers that appear in it, are:
  n   a(n)  bin(n)  {bin(s)}
  --  ----  ------  ----------------------------
   0     0       0  {0}
   1     1       1  {1}
   2     3      10  {0, 1, 10}
   3     4      11  {1, 11}
   4     7     100  {0, 1, 10, 100}
   5    11     101  {0, 1, 10, 11, 101}
   6    12     110  {0, 1, 10, 11, 110}
   7    11     111  {1, 11, 111}
   8    15    1000  {0, 1, 10, 100, 1000}
   9    24    1001  {0, 1, 10, 11, 100, 101, 1001}
  10    31    1010  {0, 1, 10, 11, 100, 101, 110, 1010}
		

Crossrefs

Programs

  • PARI
    a(n, base=2) = { my (b=digits(n, base), s=[0]); for (k=1, #b, s = setunion(s, apply(o -> base*o+b[k], s))); vecsum(s) }

Formula

A078823(n) <= a(n).
a(2^k) = 2^(k+1)-1 for any k >= 0.
a(2^k-1) = A000295(k+1) for any k >= 0.
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