A135687 a(n) = a(n-1) - A004001(n)*a(n-2), a(1) = 1, a(2) = 1.

1, 1, -1, -3, 0, 12, 12, -36, -96, 120, 792, -48, -6384, -6000, 45072, 93072, -312576, -1243296, 2195040, 17114592, -9225888, -231715584, -102553152, 3141465024, 4679762304, -42442213056, -112638647616, 566436761280, 2368655123136, -6694333057344, -44592815027520

Offset

1,4

Links

G. C. Greubel, Table of n, a(n) for n = 1..500

Formula

a(n) = a(n-1) - A004001(n)*a(n-2), with a(1) = a(2) = 1.

Mathematica

HC[n_]:= HC[n]= If[n<3, Fibonacci[n], HC[HC[n-1]] +HC[n -HC[n-1]]]; (*A004001*)
a[n_]:= a[n]= If[n<3, 1, a[n-1] - HC[n]*a[n-2]];
Table[a[n], {n, 40}]

Prog

(Sage)
@cached_function
def HC(n): # HC = A004001
    if (n<3): return fibonacci(n)
    else: return HC(HC(n-1)) +HC(n -HC(n-1))
@CachedFunction
def a(n): # A135688
    if (n<3): return 1
    else: return a(n-1) - HC(n)*a(n-2)
[a(n) for n in (1..40)] # G. C. Greubel, Nov 25 2021

Crossrefs

Cf. A004001, A135688.

Sequence in context: A071534 A336667 A269880 * A057374 A269035 A268904

Adjacent sequences: A135684 A135685 A135686 * A135688 A135689 A135690

Keyword

sign,less

Author

Roger L. Bagula, Feb 19 2008

Status

approved