A105318 -id:A105318 - cp's OEIS frontend

A187431 Numbers n that generate 5 primes under the first 5 iterations of the map n->A002731(n).

30131199, 50817201, 56496039, 74316929, 171407609, 276672151, 293315671, 337876949, 356498179, 359830101, 372590921, 432448789, 501182201, 541961069, 577016839, 616411051, 749536461, 776113741, 903321909, 919203811, 1005047121, 1285328811, 1323139751, 1340738371

Offset: 1

Zak Seidov, Apr 05 2011

nonn

Numbers n such that m=(n^2+1)/2, p=(m^2+1)/2, q=(p^2+1)/2, r=(q^2+1)/2 and s=(r^2+1)/2 are all prime.
Subsequence of A188547 which itself is subsequence of A188546 which is subsequence of A116945.
a(1)=30131199=A188547(70).
Two numbers n that generate 6 primes... are a(23)=1323139751 and a(78)=10185588801.

Charles R Greathouse IV, Table of n, a(n) for n = 1..405, replacing an earlier b-file from Zak Seidov
Stephan Baier, On the Bateman-Horn conjecture, Journal of Number Theory 96, 432-448 (2002).
Paul T. Bateman, Roger A. Horn, A heuristic asymptotic formula concerning the distribution of prime numbers, Math. Comp. 16 (1962) 363-367.

Cf. A002731, A105318, A116945, A188546, A188547.

A188546 Numbers n such that m=(n^2+1)/2, p=(m^2+1)/2 and q=(p^2+1)/2 are all prime.

Original entry on oeis.org

69, 271, 349, 3001, 3399, 4949, 6051, 9101, 9751, 10099, 10149, 11719, 12281, 15911, 22569, 24269, 25201, 25889, 28841, 31979, 37271, 39901, 42109, 44929, 46399, 48321, 50811, 60009, 63659, 63999, 71051, 71851, 75089, 76711, 87029, 96791, 103701, 110551, 111411, 112461, 113949, 125721, 126089, 127959, 129261, 131859, 132939, 137481, 144651

Offset: 1

Zak Seidov, Apr 03 2011

nonn

a(1) = 69 = A116945(5).
Numbers n that generate three primes under the first three iterations of the map n-> A002731(n).
Subsequence of A116945.

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

Cf. A002731, A105318, A116945, A188547, A187431.

r:=func< k | (k^2+1) div 2 >; [ n: n in [1..145000 by 2] | IsPrime(r(n)) and IsPrime(r(r(n))) and IsPrime(r(r(r(n)))) ];  // Bruno Berselli, Apr 05 2011

s={}; Do[If[PrimeQ[m=(n^2+1)/2] && PrimeQ[p=(m^2+1)/2] && PrimeQ[q=(p^2+1)/2], Print[n]; AppendTo[s,n]], {n,1,300000,2}]; s
mpqQ[n_]:=Module[{m=(n^2+1)/2,p},p=(m^2+1)/2;AllTrue[{m,p,(p^2+1)/2},PrimeQ]]; Select[Range[144700],mpqQ] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Apr 18 2021 *)

v=vector(10^4);i=0;forstep(n=1,9e9,2,if(isprime(m=(n^2+1)/2)&isprime(p=(m^2+1)/2)&isprime(q=(p^2+1)/2),v[i++]=n;if(i==#v,return(v)))) \\ Charles R Greathouse IV, Apr 05 2011

A188547 Numbers n such that m=(n^2+1)/2, p=(m^2+1)/2, q=(p^2+1)/2, and r=(q^2+1)/2 are all prime.

Original entry on oeis.org

4949, 6051, 169219, 183241, 560769, 1113621, 1306689, 1370269, 1421869, 1485561, 1640711, 1730709, 1876351, 1967769, 2147661, 2217351, 2293939, 2428461, 2440871, 3346661, 3625139, 3625889, 3763969, 3991209, 4020711, 4728141, 5219691, 5547221, 5554939, 5965699, 7345719, 8495879

Offset: 1

Zak Seidov, Apr 03 2011

nonn

a(1) = 4949 = A188546(6) = A116945(53).
Subsequence of A188546.
Numbers n which generate 4 primes under the first four iterations of the map n-> A002731(n).
Among first 10000 terms, there are 1072 primes, the first a(3) = 169219 and the last a(10000) = 16541600731. - Zak Seidov, Jan 16 2019

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000, replacing an earlier file from Zak Seidov

Cf. A002731, A105318, A116945, A188546, A187431.

r:=func< k | (k^2+1) div 2 >; [ n: n in [1..1000000 by 2] | IsPrime(r(n)) and IsPrime(r(r(n))) and IsPrime(r(r(r(n))))and IsPrime(r(r(r(r(n)))))]; // Vincenzo Librandi, Jan 16 2019

s={}; Do[If[PrimeQ[m=(n^2+1)/2] && PrimeQ[p=(m^2+1)/2] && PrimeQ[q=(p^2+1)/2] && PrimeQ[r=(q^2+1)/2], AppendTo[s,n]], {n,1,10000000,2}]; s

v=vector(10^4); i=0; forstep(n=1, 9e99, 2, if(isprime(m=(n^2+1)/2) && isprime(p=(m^2+1)/2) && isprime(q=(p^2+1)/2) && isprime(r=(q^2+1)/2), v[i++]=n; if(i==#v, return))) \\ Charles R Greathouse IV, Apr 12 2011

A077034 a(1)=3; a(2n), a(2n+1) are smallest integers > a(2n-1) such that a(2n-1)^2+a(2n)^2=a(2n+1)^2.

Original entry on oeis.org

3, 4, 5, 12, 13, 84, 85, 132, 157, 12324, 12325, 15960, 20165, 26280, 33125, 79500, 86125, 95400, 128525, 152040, 199085, 477804, 517621, 871500, 1013629, 513721874820, 513721874821, 4351526469072, 4381745402885, 10516188966924, 11392538047501

Offset: 1

Zak Seidov, Oct 21 2002

nonn

Note that each time two more terms are added simultaneously. The sequence is infinite.
Smallest sequence of Pythagorean triples {a(k-1),a(k),a(k+1)},with k=2n,such that the hypotenuse of one triangle is the short leg of the next one. Such a sequence is called 2-prime Pythagorean because only the first two triangles (3,4,5),(5,12,13) both have prime hypotenuse and short leg. The next such sequence is given by A076604. Actually, the starting terms for all 2-prime and 3-prime Pythagorean triangles are given respectively by A048270 and A048295. The starting term for the smallest n-prime Pythagorean triangle is A105318. - Lekraj Beedassy, Sep 16 2005
a(2n) <= (a(2n-1)^2-1)/2; a(2n+1) <= (a(2n-1)^2+1)/2. [Max Alekseyev, May 11 2011]

			a(1)=3 implies a(2)=4 and a(3)=5: 3^2+4^2=5^2.
a(3)=5 implies a(4)=12 and a(5)=13: 5^2+12^2=13^2.

Cf. A048270, A048295, A076604, A105318.

More terms from Max Alekseyev, May 11 2011

cp's OEIS Frontend

A187431 Numbers n that generate 5 primes under the first 5 iterations of the map n->A002731(n).

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A188546 Numbers n such that m=(n^2+1)/2, p=(m^2+1)/2 and q=(p^2+1)/2 are all prime.

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A188547 Numbers n such that m=(n^2+1)/2, p=(m^2+1)/2, q=(p^2+1)/2, and r=(q^2+1)/2 are all prime.

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A077034 a(1)=3; a(2n), a(2n+1) are smallest integers > a(2n-1) such that a(2n-1)^2+a(2n)^2=a(2n+1)^2.

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