OFFSET
0,7
COMMENTS
Shifts 5 places left when convolved with itself.
LINKS
Seiichi Manyama, Table of n, a(n) for n = 0..5000
FORMULA
G.f.: 1/(1 - x/(1 - x^5/(1 - x^5/(1 - x/(1 - x^5/(1 - x^5/(1 - x/(1 - x^5/(1 - x^5/(1 - ...)))))))))), a continued fraction.
Recurrence: a(n+5) = Sum_{k=0..n} a(k)*a(n-k).
EXAMPLE
G.f.: A(x) = 1 + x + x^2 + x^3 + x^4 + x^5 + 2*x^6 + 3*x^7 + 4*x^8 + 5*x^9 + 6*x^10 + ...
MAPLE
a:= proc(n) option remember; `if`(n<5, 1,
add(a(j)*a(n-5-j), j=0..n-5))
end:
seq(a(n), n=0..50); # Alois P. Heinz, May 08 2019
MATHEMATICA
terms = 47; A[_] = 0; Do[A[x_] = 1 + x + x^2 + x^3 + x^4 + x^5 A[x]^2 + O[x]^(terms + 1) // Normal, terms + 1]; CoefficientList[A[x], x]
a[n_] := a[n] = Sum[a[k] a[n - k - 5], {k, 0, n - 5}]; a[0] = a[1] = a[2] = a[3] = a[4] = 1; Table[a[n], {n, 0, 47}]
PROG
(SageMath)
@CachedFunction
def a(n): # a = A307972
if (n<5): return 1
else: return sum(a(k)*a(n-k-5) for k in range(n-4))
[a(n) for n in range(51)] # G. C. Greubel, Nov 26 2022
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, May 08 2019
STATUS
approved