login
A305574
Number of primitive (1,1) pairs in the Fibonacci tree at depth 3n.
1
5, 2, 7, 30, 143, 728, 3876, 21318, 120175, 690690, 4032015, 23841480, 142498692, 859515920, 5225264024, 31983672534, 196947587823, 1219199353190, 7583142491925, 47365474641870, 296983176369495, 1868545312633440, 11793499763070480, 74650344244967400
OFFSET
1,1
REFERENCES
John Charles Saunders, Problems in Combinatorial and Analytic Number Theory, Ph. D. thesis, University of Waterloo, 2018.
LINKS
Kevin G. Hare, and J. C. Saunders, On (a,b) Pairs in Random Fibonacci Sequences, Arxiv preprint arXiv:1608.03522 [math.NT], February 2018.
PROG
(PARI) {a(n) = my(A); if( n<=1, 5*(n==1), A = O(x); for(k=1, n, A = x / (1 - A)^2); polcoeff(A, n))}; /* Michael Somos, Dec 10 2019 */
CROSSREFS
Cf. A006013.
Sequence in context: A198130 A309773 A241388 * A248259 A128666 A013674
KEYWORD
nonn
AUTHOR
Jeffrey Shallit, Jun 05 2018
EXTENSIONS
More terms added and a(14) corrected by Michael Somos, Dec 10 2019
STATUS
approved