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A135687 a(n) = a(n-1) - A004001(n)*a(n-2), a(1) = 1, a(2) = 1. 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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified January 29 14:59 EST 2023. Contains 359923 sequences. (Running on oeis4.)