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%I #7 Feb 14 2016 14:57:04
%S 0,1,6,13,26,58,72,107,160,230,286,440,558,599,696,851,1032,1298,1510,
%T 1826,2122,2353,2624,3294,3884,4335,4870,5001,5242,5722,6048,6699,
%U 7424,8226,8990,10166,11226,12069,13048,14384,15664,16885,18134,19071,20094,21276,22360,25150,27788,30091,32582,34343,36262
%N Convolution of A006068 (inverse of Gray code) with itself: a(n) = Sum_{k=1..n+1} A006068(k) * A006068(1+n-k).
%H Antti Karttunen, <a href="/A268721/b268721.txt">Table of n, a(n) for n = 0..1023</a>
%F a(n) = Sum_{k=1..n+1} A006068(k) * A006068(1+n-k).
%o (Scheme)
%o (define A268721 (CONVOLVE 1 A006068 A006068)) ;; This version requires _Antti Karttunen_'s IntSeq-library.
%o ;; More stand-alone version:
%o (define (A268721 n) (add (lambda (k) (* (A006068 k) (A006068 (- (+ n 1) k)))) 1 (+ n 1)))
%o (define (add intfun lowlim uplim) (let sumloop ((i lowlim) (res 0)) (cond ((> i uplim) res) (else (sumloop (1+ i) (+ res (intfun i)))))))
%Y Antidiagonal sums of array A268724.
%Y Cf. A006068
%K nonn
%O 0,3
%A _Antti Karttunen_, Feb 13 2016
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