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A181093 p*(p+2)/3 where p and p+4 are primes. 0
5, 21, 65, 133, 481, 645, 1541, 2133, 3201, 3605, 4033, 5461, 8965, 12545, 16725, 17633, 25761, 31621, 32865, 40833, 48133, 52801, 64533, 69921, 71765, 79381, 83333, 125665, 138245, 151425, 182533, 191521, 197633, 226325, 243105, 246533, 256961, 260485, 274821 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

For p>3, p == 1 mod 6 and p(p+2) == 0 mod 3, hence, except for the first term, a(n) = subsequence of A014641 Odd octagonal numbers: (2n+1)(6n+1).

LINKS

Table of n, a(n) for n=1..39.

EXAMPLE

p=3,p+4=7 are primes and a(1)=3*5/3=3,

p=7,p+4=11 are primes and a(2)=7*9/3=21=A014641(2),

p=13,p+4=17 are primes and a(3)=13*15/3=65=A014641(3).

MATHEMATICA

# (# + 2)/3 & /@ Select[Prime@Range@140, PrimeQ[# + 4] &]

PROG

(PARI) {forprime (p=3, 10^3, isprime(p+4)&print1(p*(p+2)/3, ", "))}

CROSSREFS

Cf. A014641.

Sequence in context: A342379 A146822 A146223 * A055384 A271540 A272987

Adjacent sequences:  A181090 A181091 A181092 * A181094 A181095 A181096

KEYWORD

nonn

AUTHOR

Zak Seidov, Jan 23 2011

EXTENSIONS

More terms from Michel Marcus, Mar 04 2014

STATUS

approved

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Last modified June 22 21:29 EDT 2021. Contains 345393 sequences. (Running on oeis4.)