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A126590 Multiples of 3 or 5 but not both. 3
3, 5, 6, 9, 10, 12, 18, 20, 21, 24, 25, 27, 33, 35, 36, 39, 40, 42, 48, 50, 51, 54, 55, 57, 63, 65, 66, 69, 70, 72, 78, 80, 81, 84, 85, 87, 93, 95, 96, 99, 100, 102, 108, 110, 111, 114, 115, 117, 123, 125, 126, 129, 130, 132, 138, 140, 141, 144, 145, 147, 153, 155, 156 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Numbers n such that (n mod 3)*(n mod 5) = 0 and n mod 15 > 0.

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

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

FORMULA

a(n) = a(n-1) + a(n-6) - a(n-7). - Charles R Greathouse IV, Oct 11 2013

EXAMPLE

3, 5, 6, 9, 10, 12, (not 15), 18, 20, 21, 24, 25, 27, (not 30), 33, etc.

MATHEMATICA

s={}; Do[m3=Mod[n, 3]; m5=Mod[n, 5]; m15=Mod[n, 15]; If[m3*m5==0&&m15>0, AppendTo[s, n]], {n, 200}]; s

PROG

(PARI) is(n)=isprime(gcd(n, 15)) \\ Charles R Greathouse IV, Oct 11 2013

(MAGMA) I:=[3, 5, 6, 9, 10, 12, 18]; [n le 7 select I[n] else Self(n-1) + Self(n-6) - Self(n-7): n in [1..70]]; // G. C. Greubel, Mar 06 2018

CROSSREFS

Cf. A126073, A126592.

Sequence in context: A281746 A287162 A018900 * A140584 A085705 A187417

Adjacent sequences:  A126587 A126588 A126589 * A126591 A126592 A126593

KEYWORD

nonn,easy

AUTHOR

Zak Seidov, Mar 13 2007

STATUS

approved

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Last modified November 14 04:56 EST 2019. Contains 329110 sequences. (Running on oeis4.)