The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A213626 (Bold, blue-underlined text is an addition; faded, red-underlined text is a ~~deletion~~.)
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A213626

a(n) = Sum_{0<=i<j<k<=n} b(i)*b(j)*b(k), where b(m) = A020985(m).
(history; published version)

#32 by Alois P. Heinz at Sun Feb 12 11:31:49 EST 2023

STATUS

reviewed

approved

#31 by Joerg Arndt at Sun Feb 12 11:31:20 EST 2023

STATUS

proposed

reviewed

#30 by Chai Wah Wu at Sun Feb 12 11:24:09 EST 2023

STATUS

editing

proposed

#29 by Chai Wah Wu at Sun Feb 12 11:24:00 EST 2023

PROG

(Python)

def A213626(n): return sum((-1 if (i&(i>>1)).bit_count()&1 else 1)*sum((-1 if (j&(j>>1)).bit_count()&1 else 1)*sum(-1 if (k&(k>>1)).bit_count()&1 else 1 for k in range(j+1, n+1)) for j in range(i+1, n+1)) for i in range(n+1)) # Chai Wah Wu, Feb 12 2023

STATUS

approved

editing

#28 by Alois P. Heinz at Wed Jun 01 08:58:41 EDT 2022

STATUS

proposed

approved

#27 by Jean-François Alcover at Wed Jun 01 06:15:58 EDT 2022

STATUS

editing

proposed

#26 by Jean-François Alcover at Wed Jun 01 06:15:55 EDT 2022

MATHEMATICA

b[n_] := b[n] = Module[{q, r}, If[n==0, 1, {q, r}=QuotientRemainder[n, 2]; If[r == 0, b[q], b[q]*(-1)^q]]];

s[j_] := s[j] = If[j < 0, 0, s[j-1] + b[j]];

t[k_] := t[k] = If[k < 1, 0, t[k-1] + b[k]*s[k-1]];

a[n_] := a[n] = If[n < 2, 0, a[n-1] + b[n]*t[n-1]];

Table[a[n], {n, 0, 100}] (* Jean-François Alcover, Jun 01 2022, after Alois P. Heinz *)

STATUS

approved

editing

#25 by Alois P. Heinz at Sun Nov 23 17:05:15 EST 2014

STATUS

editing

approved

#24 by Alois P. Heinz at Sun Nov 23 17:05:11 EST 2014

MAPLE

seq (a(n), n=0..100);

STATUS

approved

editing

#23 by Alois P. Heinz at Mon Jan 27 09:45:00 EST 2014

STATUS

editing

approved