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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A174605 Partial sums of A011371.

Original entry on oeis.org

0, 0, 1, 2, 5, 8, 12, 16, 23, 30, 38, 46, 56, 66, 77, 88, 103, 118, 134, 150, 168, 186, 205, 224, 246, 268, 291, 314, 339, 364, 390, 416, 447, 478, 510, 542, 576, 610, 645, 680, 718, 756, 795, 834, 875, 916, 958, 1000, 1046, 1092, 1139, 1186, 1235, 1284, 1334
Offset: 0

Views

Author

Jonathan Vos Post, Mar 23 2010

Keywords

Comments

Exponent of 2 in the superfactorials, i.e., a(n) = A007814(A000178(n)). - Ralf Stephan, Jan 03 2014

Crossrefs

Cf. A000120, A011371 (first differences).
Cf. A000178 (superfactorials), A007814 (2-adic valuation), A272011 (binary exponents).
Cf. A249152 (hyperfactorial valuation), A187059 (binomial valuation), A173345 (superfactorial 10-valuation).

Programs

  • Maple
    a:= proc(n) option remember; `if`(n<1, 0,
          a(n-1)+n-add(i, i=Bits[Split](n)))
        end:
    seq(a(n), n=0..54);  # Alois P. Heinz, Oct 30 2021
  • Mathematica
    Accumulate[Table[n-DigitCount[n,2,1],{n,0,130}]] (* Harvey P. Dale, Feb 26 2015 *)
    a[n_] := IntegerExponent[BarnesG[n + 2], 2]; Array[a, 100, 0] (* Amiram Eldar, Aug 08 2024 *)
  • PARI
    a(n) = n++; my(v=binary(n),t=#v-1); for(i=1,#v, if(v[i],v[i]=t++,t--)); (n^2 - fromdigits(v,2))>>1; \\ Kevin Ryde, Oct 29 2021
    
  • Python
    def A174605(n): return (n*(n+1)>>1)-(n+1)*n.bit_count()-(sum((m:=1<>j)-(r if n<<1>=m*(r:=k<<1|1) else 0)) for j in range(1,n.bit_length()+1))>>1)  # Chai Wah Wu, Nov 12 2024

Formula

a(n) = Sum_{i=0..n} A011371(i).
From Kevin Ryde, Oct 29 2021: (Start)
a(n) = n*(n+1)/2 - A000788(n).
a(n) ~ (n^2)/2 + O(n*log_2(n)). [Lagarias and Mehta, theorem 4.2 with p=2]
a(n) = ( (n+1)^2 - Sum_{i=1..k} (e[i]+2*i-1) * 2^e[i] )/2, where binary expansion n+1 = 2^e[1] + ... + 2^e[k] with descending exponents e[1] > e[2] > ... > e[k] (A272011).
(End)
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