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Search: id:A152916
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| A152916 |
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Tetrahedral numbers composed of two primes and one nonprime. |
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+0
1
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| 1, 4, 10, 35, 286, 969, 4495, 12341, 35990, 62196, 176851, 209934, 437989, 562475, 971970, 1179616, 1293699, 1975354, 2303960, 3280455, 3737581, 5061836, 7023974, 12347930, 13436856, 16435111, 23706021, 30865405, 35999900, 39338069
(list; graph; listen)
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OFFSET
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1,2
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FORMULA
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a(n)=A000292(A124588(n-1)), n>1. [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Aug 14 2009]
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EXAMPLE
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If n=1(nonprime), n+1=2(prime) and n+2=3(prime), then 1*2*3/6=1=a(1). If n+1=2(prime), n+2=3(prime) and n+3=4(nonprime), then 2*3*4/6=4=a(2). If n+2=3(prime), n+3=4(nonprime) and n+4=5(prime), then 3*4*5/6=10=a(3). If n+4=5(prime), n+5=6(nonprime) and n+6=7(prime), then 5*6*7/6=35=a(4). If n+10=11(prime), n+11=12(nonprime) and n+12=13(prime), then 11*12*13/6=286=a(5), etc.
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MAPLE
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A000292 := proc(n) n*(n+1)*(n+2)/6; end: for n from 1 to 800 do ps := 0 ; if isprime(n) then ps := ps+1 ; fi; if isprime(n+1) then ps := ps+1 ; fi; if isprime(n+2) then ps := ps+1 ; fi; if ps = 2 then printf("%d, ", A000292(n)) ; fi; od: [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Aug 14 2009]
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CROSSREFS
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Cf. A000040, A000392, A141468, A152622.
Sequence in context: A059710 A149177 A149178 this_sequence A108596 A088013 A149179
Adjacent sequences: A152913 A152914 A152915 this_sequence A152917 A152918 A152919
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KEYWORD
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nonn
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AUTHOR
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Juri-Stepan Gerasimov (2stepan(AT)rambler.ru), Dec 15 2008
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