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A241607 Semiprimes generated by the polynomial (1/4)* (n^5 - 133*n^4 + 6729*n^3 - 158379*n^2 + 1720294*n - 6823316). 1
5141923, 6084557, 11403823, 13201987, 17488411, 20017609, 33239291, 37446979, 42070423, 47139347, 72512623, 88747907, 118408673, 129881707, 169708339, 184952323, 201267887, 278376073, 324881567, 406044923, 436421497, 538566199, 616639427, 658920007, 750410069 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

(1/4)* (n^5 - 133*n^4 + 6729*n^3 - 158379*n^2 + 1720294*n - 6823316) is a well known prime producing polynomial found by Shyam Sunder Gupta, which generates 57 distinct primes for n = 0,1,...55,56.

For n =  57, this polynomial yields the first semiprime:  5141923 = 821 * 6263.

LINKS

K. D. Bajpai, Table of n, a(n) for n = 1..10000

EXAMPLE

For n=57: (1/4)* (n^5 - 133*n^4 + 6729*n^3 - 158379*n^2 + 1720294*n - 6823316) = 5141923 = 821 * 6263, which is a semiprime and is included in the sequence.

For n=58: (1/4)* (n^5 - 133*n^4 + 6729*n^3 - 158379*n^2 + 1720294*n - 6823316) = 6084557 = 131 * 46447, which is a semiprime and is included in the sequence.

MAPLE

with(numtheory): KD:= proc() local a, b, k; k:=(1/4)*(n^5 - 133*n^4 + 6729*n^3 - 158379*n^2 + 1720294*n - 6823316); a:=bigomega(k); if a=2 then RETURN (k); fi; end: seq(KD(), n=0..200);

MATHEMATICA

A241607 = {}; Do[k= (1/4) * (n^5 - 133 * n^4 + 6729 * n^3 - 158379 * n^2 + 1720294 * n - 6823316); If[PrimeOmega[k] ==2, AppendTo[A241607, k]], {n, 200}]; A241607

(*For the b-file:*) n=0; Do[t=((1/4) * (k^5 - 133 * k^4 + 6729 * k^3 - 158379 * k^2 + 1720294 * k - 6823316)); If[PrimeOmega[t]==2, n++; Print[n, " ", t]], {k, 10^6}]

PROG

(PARI) s=[]; for(n=1, 200, t=(1/4)*(n^5-133*n^4+6729*n^3-158379*n^2+1720294*n-6823316); if(bigomega(t)==2, s=concat(s, t))); s \\ Colin Barker, Apr 26 2014

CROSSREFS

Cf. A007641 (for primes).

Cf. A001358, A072381, A082919, A121887, A145292, A228183, A237627.

Sequence in context: A186624 A157844 A263039 * A140658 A172715 A257153

Adjacent sequences:  A241604 A241605 A241606 * A241608 A241609 A241610

KEYWORD

nonn

AUTHOR

K. D. Bajpai, Apr 26 2014

STATUS

approved

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Last modified November 15 01:25 EST 2019. Contains 329143 sequences. (Running on oeis4.)