OFFSET
1,1
LINKS
Amy Glen, Jamie Simpson, and W. F. Smyth, Counting Lyndon Factors, Electronic Journal of Combinatorics 24(3) (2017), #P3.28.
Ryo Hirakawa, Yuto Nakashima, Shunsuke Inenaga, and Masayuki Takeda, Counting Lyndon Subsequences, arXiv:2106.01190 [math.CO], 2021. See MDF(n, s).
FORMULA
a(n) = binomial(n+1,2) - (s-p)*binomial(m+1,2) - p*binomial(m+2,2) + s where s=5, m=floor(n/s), p=n-m*s. - Andrew Howroyd, Aug 14 2017
Conjectures from Colin Barker, Oct 03 2017: (Start)
G.f.: x*(5 - 4*x + x^2 + x^3 + x^4 - 5*x^5 + 5*x^6) / ((1 - x)^3*(1 + x + x^2 + x^3 + x^4)).
a(n) = 2*a(n-1) - a(n-2) + a(n-5) - 2*a(n-6) + a(n-7) for n>6.
(End)
PROG
(PARI) a(n)=(s->my(m=n\s, p=n%s); binomial(n+1, 2)-(s-p)*binomial(m+1, 2)-p*binomial(m+2, 2)+s)(5); \\ Andrew Howroyd, Aug 14 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Aug 11 2017
EXTENSIONS
a(11)-a(55) from Andrew Howroyd, Aug 14 2017
STATUS
approved