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A060824 4-wave sequence beginning with 2s. 0
2, 2, 2, 2, 4, 6, 8, 14, 18, 20, 38, 52, 60, 112, 150, 170, 320, 432, 492, 924, 1244, 1414, 2658, 3582, 4074, 7656, 10314, 11728, 22042, 29698, 33772, 63470, 85512, 97240, 182752, 246222, 279994, 526216, 708968, 806208, 1515176, 2041392, 2321386 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,1

COMMENTS

Primes are the numbers >=2 which have no nontrivial divisor: a(p)=0.

Also: a(n)= A032741(n)-1, n>=2 (from number of divisors <n, called proper divisors).

LINKS

Table of n, a(n) for n=2..44.

F. v. Lamoen, Wave sequences

Index entries for linear recurrences with constant coefficients, signature (1, -1, 3, -3, 3, 0, 0, 0, -1, 1, -1).

FORMULA

a(n) = 2*A038197(n-2).

a(n)=2*a(n-3)+3*a(n-6)-a(n-9)-a(n-12) - Antonio G. Astudillo (afg_astudillo(AT)hotmail.com), Jan 12 2003

G.f.: -2*x^2*(x^5-2*x^4+2*x^3-x^2-1)/((x^2-x+1)*(x^9-3*x^3+1)). - Colin Barker, Nov 09 2012

CROSSREFS

Cf. A038197.

Sequence in context: A126663 A032600 A103260 * A244459 A064849 A269302

Adjacent sequences:  A060821 A060822 A060823 * A060825 A060826 A060827

KEYWORD

easy,nonn

AUTHOR

Jason Earls, May 01 2001

STATUS

approved

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Last modified January 20 14:40 EST 2019. Contains 319333 sequences. (Running on oeis4.)