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A373087
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k is term if k is a square and its odd part is divisible by exactly two distinct primes.
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2
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225, 441, 900, 1089, 1225, 1521, 1764, 2025, 2601, 3025, 3249, 3600, 3969, 4225, 4356, 4761, 4900, 5625, 5929, 6084, 7056, 7225, 7569, 8100, 8281, 8649, 9025, 9801, 10404, 12100, 12321, 12996, 13225, 13689, 14161, 14400, 15129, 15876, 16641, 16900, 17424, 17689, 18225
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OFFSET
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1,1
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COMMENTS
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LINKS
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FORMULA
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a(n) = Sum_{k=2..n+3} LegendreSymbol(n, prime(k)).
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EXAMPLE
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8100 is term because (8100 / 2^2) = 3^4 * 5^2.
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MAPLE
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isA := k -> issqr(k) and nops(NumberTheory:-PrimeFactors(k/2^padic[ordp](k, 2))) = 2: A := select(isA, [seq(1..19000)]);
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MATHEMATICA
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Select[Range[200]^2, PrimeNu[#/2^IntegerExponent[#, 2]] == 2 &] (* Paolo Xausa, Jul 10 2024 *)
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PROG
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(PARI) isok(k) = issquare(k) && (omega(k/2^valuation(k, 2)) == 2); \\ Michel Marcus, May 31 2024
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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