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A226562 Numbers which are the sum of two squared primes in exactly three ways (ignoring order). 3
2210, 3770, 5330, 6290, 12818, 16490, 18122, 19370, 24050, 24650, 26690, 32810, 33410, 34970, 36530, 39650, 39770, 44642, 45050, 45890, 49010, 50690, 51578, 57770, 59450, 61610, 63050, 66170, 67490, 72410, 73610, 74210, 80330, 85202, 86210, 86330, 88010 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Suggestion: difference between successive terms is always at least 3. (With the known 115885 terms <10^9, the smallest difference is 24.) - Zak Seidov, Jun 12 2013

REFERENCES

Stan Wagon, Mathematica in Action, Springer, 2000 (2nd ed.), Ch. 17.5, pp. 375-378.

LINKS

Zak Seidov, Table of n, a(n) for n = 1..2464 (all terms up to 10^7).

EXAMPLE

2210 = 19^2 + 43^2 = 23^2 + 41^2 = 29^2 + 37^2;

MAPLE

Prime2PairsSum := s -> select( x -> `if`(andmap(isprime, x), true, false), numtheory:-sum2sqr(s)):

for n from 2 to 10 do

if nops(Prime2PairsSum(n)) = 3 then print(n, Prime2PairsSum(n)) fi

od;

MATHEMATICA

Select[Range@20000, Length[Select[ PowersRepresentations[#, 2, 2], And @@ PrimeQ[#] &]] == 3 &] (* Giovanni Resta, Jun 11 2013 *)

CROSSREFS

Cf. A054735 (restricted to twin primes), A037073, A069496.

Cf. A045636 (sum of two squared primes), A226539.

Cf. A214511 (least number having n representations).

Cf. A226539 (restricted to sums decomposed in exactly three ways).

Sequence in context: A043659 A178458 A248712 * A300166 A031772 A305880

Adjacent sequences:  A226559 A226560 A226561 * A226563 A226564 A226565

KEYWORD

nonn

AUTHOR

Henk Koppelaar, Jun 11 2013

EXTENSIONS

a(22)-a(37) from Giovanni Resta, Jun 11 2013

STATUS

approved

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Last modified October 21 14:13 EDT 2019. Contains 328301 sequences. (Running on oeis4.)