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 A195324 Even numbers that cannot be represented as the sum of an odd prime and a safe prime (A005385). 1
 2, 4, 6, 32, 56, 92, 98, 122, 128, 140, 152, 176, 194, 212, 224, 242, 254, 260, 272, 296, 302, 308, 326, 332, 368, 392, 398, 410, 422, 434, 452, 458, 476, 488, 500, 512, 518, 524, 536, 542, 560, 572, 596, 602, 632, 644, 656, 662, 674, 686, 692, 704, 710, 728 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Reinhard Zumkeller, Table of n, a(n) for n = 1..10000 StackExchange, Even numbers greater than 6 as sum of two specific primes MATHEMATICA mx = 1000; safe = Select[Prime[Range[PrimePi[mx]]], PrimeQ[(# - 1)/2] &]; p = Prime[Range[2, PrimePi[mx]]]; Complement[Range[2, mx, 2], Union[Flatten[Outer[Plus, p, t]]]] (* T. D. Noe, Sep 15 2011 *) PROG #!/usr/bin/perl \$| = 1; sub is_prime { my \$n = shift; return 0 if \$n < 2; return 1 if \$n == 2; return 0 unless \$n % 2; my \$sn = int(sqrt(\$n)); for (my \$j = 3; \$j <= \$sn; \$j += 2) { return 0 if \$n % \$j == 0; } return 1; } my \$n = 0; while (1) { ++\$n; next if \$n % 2; my \$found = 0; for my \$p (3 .. \$n) { next unless \$p % 2; my \$q = \$n - \$p; next unless \$q % 2; next unless is_prime(\$p); next unless is_prime(\$q); next unless is_prime((\$p - 1) / 2) || is_prime((\$q - 1) / 2); \$found = 1; last; } print "\$n\n" unless \$found; } (Haskell) a195324 n = a195324_list !! (n-1) a195324_list = filter p [2, 4..] where p n = all ((== 0) . a010051) \$ takeWhile (> 1) \$ map (n -) a005385_list -- Reinhard Zumkeller, Sep 18 2011 CROSSREFS Cf. A000040 (primes), A005385 (safe primes). Sequence in context: A100838 A056696 A045662 * A175877 A269265 A173818 Adjacent sequences: A195321 A195322 A195323 * A195325 A195326 A195327 KEYWORD nonn AUTHOR Dan Brumleve, Sep 15 2011 STATUS approved

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Last modified April 14 07:36 EDT 2024. Contains 371655 sequences. (Running on oeis4.)