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.
%I A278216 #17 Sep 11 2022 12:11:58
%S A278216 4,0,0,4,0,0,1,0,3,1,0,3,0,0,0,2,2,0,2,2,0,1,0,0,4,0,0,3,0,0,2,0,2,0,
%T A278216 0,4,0,0,1,2,1,1,0,3,0,1,0,0,3,0,1,3,0,1,1,0,3,0,0,3,0,0,0,3,1,0,2,2,
%U A278216 0,0,1,1,2,1,1,2,0,0,1,0,3,1,0,3,0,1,0,1,3,0,1,2,0,1,0,1,2,0,0,4,0,0,2,0,2,1,0,3,1,0,0,2,1,0,1,3,0,1,0,0,4
%N A278216 Number of children that node n has in the tree defined by the edge relation A255131(child) = parent, "the least squares beanstalk".
%H A278216 Antti Karttunen, <a href="/A278216/b278216.txt">Table of n, a(n) for n = 0..10000</a>
%F A278216 a(n) = Sum_{i=0..4} [A002828(n+i) = i]. (Here [ ] is the Iverson bracket, giving as its result 1 only if A002828(n+i) is i, otherwise zero.)
%e A278216 a(0) = 4 as 0 - A002828(0) = 0, 1 - A002828(1) = 0, 2 - A002828(2) = 0 and 3 - A002828(3) = 0. (But 4 - A002828(4) = 3.) Note that 0 is the only number which is its own child as 0 - A002828(0) = 0.
%o A278216 (Scheme) (define (A278216 n) (let loop ((s 0) (k (+ 4 n))) (if (< k n) s (loop (+ s (if (= n (A255131 k)) 1 0)) (- k 1)))))
%Y A278216 Cf. A002828, A255131, A276573.
%Y A278216 Cf. A278490 (positions of zeros), A278489 (positions of nonzeros), A278491 (positions of 4's).
%K A278216 nonn
%O A278216 0,1
%A A278216 _Antti Karttunen_, Nov 25 2016