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 A226539 Numbers which are the sum of two squared primes in exactly two ways (ignoring order). 3
 338, 410, 578, 650, 890, 1010, 1130, 1490, 1730, 1802, 1898, 1970, 2330, 2378, 2738, 3050, 3170, 3530, 3650, 3842, 3890, 4010, 4658, 4850, 5018, 5090, 5162, 5402, 5450, 5570, 5618, 5690, 5858, 6170, 6410, 6530, 6698, 7010, 7178, 7202, 7250, 7850, 7970, 8090 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 REFERENCES Stan Wagon, Mathematica in Action, Springer, 2000 (2nd ed.), Ch. 17.5, pp. 375-378. LINKS T. D. Noe, Table of n, a(n) for n = 1..10000 EXAMPLE 338 = 7^2 + 17^2 = 13^2 + 13^2; 410 = 7^2 + 19^2 = 11^2 + 17^2. MAPLE Prime2PairsSum := p -> select(x ->`if`(andmap(isprime, x), true, false), numtheory:-sum2sqr(p)): for n from 2 to 10^6 do if nops(Prime2PairsSum(n)) = 2 then print(n, Prime2PairsSum(n)) fi; od; MATHEMATICA Select[Range@10000, Length[Select[ PowersRepresentations[#, 2, 2], And @@ PrimeQ[#] &]] == 2 &] (* Giovanni Resta, Jun 11 2013 *) PROG (PARI) select( is_A226539(n)={#[0|t<-sum2sqr(n), isprime(t[1])&&isprime(t[2])]==2}, [1..10^4]) \\ For more efficiency, apply selection to A045636. See A133388 for sum2sqr(). - M. F. Hasler, Dec 12 2019 CROSSREFS Cf. A054735 (restricted to twin primes), A037073, A069496. Cf. A045636 (sum of two squared primes: a superset). Cf. A214511 (least number having n representations). Cf. A226562 (restricted to sums decomposed in exactly three ways). Sequence in context: A084231 A243483 A234625 * A066478 A261707 A202443 Adjacent sequences: A226536 A226537 A226538 * A226540 A226541 A226542 KEYWORD nonn AUTHOR Henk Koppelaar, Jun 10 2013 EXTENSIONS a(25)-a(44) from Giovanni Resta, Jun 11 2013 STATUS approved

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Last modified September 28 13:18 EDT 2023. Contains 365735 sequences. (Running on oeis4.)