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A253108 Numbers n such that (sum of n^2 through (n+2)^2) + (n+1)^2 is prime. 1
2, 4, 6, 9, 14, 17, 20, 21, 25, 32, 34, 35, 40, 45, 49, 51, 52, 56, 60, 62, 65, 76, 80, 82, 86, 87, 89, 94, 95, 96, 100, 104, 105, 107, 112, 114, 115, 116, 117, 124, 126, 135, 137, 140, 145, 147, 151, 164, 167, 172, 174, 179, 180, 181, 182, 199, 200, 202, 205, 206, 207 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Sequence is related to the Legendre conjecture.

No terms == 3 mod 5 or == 1 mod 7 or 0 mod 11. - Robert Israel, Jun 24 2015

LINKS

Robert Israel, Table of n, a(n) for n = 1..10000

EXAMPLE

For n=2, n+1=3, n+2=4: we have

Sum(n^2,(n+1)^2)=Sum(2^2,3^2)=Sum(4,9)=Sum(4+5+6+7+8+9)=39,

Sum((n+1)^2,(n+2)^2)=Sum(3^2,4^2)=Sum(9,16)=Sum(9+10+11+12+13+14+15+16)=100,

39+100=139,

139 is prime; hence 2 is a term.

MAPLE

select(n -> isprime(4*n^3+14*n^2+20*n+11), [$1..1000]); # Robert Israel, Dec 28 2014

PROG

(PARI)for (n=1, 1000, if(isprime(4*n^3+14*n^2+20*n+11), print1(n", ")))

CROSSREFS

Sequence in context: A081225 A164140 A205883 * A198201 A281989 A328423

Adjacent sequences:  A253105 A253106 A253107 * A253109 A253110 A253111

KEYWORD

nonn

AUTHOR

César Aguilera, Dec 26 2014

EXTENSIONS

a(47) corrected by Robert Israel, Jun 24 2015

STATUS

approved

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Last modified September 28 05:33 EDT 2020. Contains 337392 sequences. (Running on oeis4.)