A236381 Smallest value of x such that x^2 + y^2 = P, where P is the product of the first n primes of the form 4k + 1, and 0 < x < y.

1, 1, 4, 2, 64, 59, 1342, 1076, 4268, 10739, 64387, 818998, 3226976, 26444853, 53155423, 1175849126, 13396689992, 2368807981, 907313696551, 483703442648, 2835669288809, 98713800566163

Offset

1,3

Links

Table of n, a(n) for n=1..22.

Example

a(3) = 4 because the solutions to x^2 + y^2 = 5*13*17 are (x,y) = (23,24), (9,32), (4,33), (12,31) of which the smallest value of x is 4.

Prog

(PARI) prd(n) = my(q=3, t=1); for(k=1, n, until(q%4==1, q=nextprime(q+1)); t*=q); t; \\ A006278
a(n) = {my(t=prd(n), q=0); until(issquare(t-q^2), q++); q; } \\ Michel Marcus, Mar 05 2021

Crossrefs

Cf. A002144, A006278, A236382.

Sequence in context: A163176 A277306 A201444 * A335300 A201228 A010319

Adjacent sequences: A236378 A236379 A236380 * A236382 A236383 A236384

Keyword

nonn,more

Author

Colin Barker, Jan 24 2014

Status

approved