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 A229960 Primes of the form n^3 - T(n) - 1 where T(n) is the n-th triangular number. 1
 53, 109, 683, 4759, 7789, 9029, 13523, 15299, 45989, 63179, 68059, 90089, 116423, 174019, 225089, 370619, 610469, 700963, 994949, 1025149, 1119403, 1398599, 1594709, 1898873, 2291189, 2561899, 2734129, 2975543, 3038039, 3296773, 3784169, 3857489, 5913269, 6212483 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Also primes of the form (2*n^3 - n^2 - n - 2)/2. LINKS K. D. Bajpai, Table of n, a(n) for n = 1..10000 EXAMPLE a(2) = 109 since 5^3 - T(5) - 1 = 125 - 15 - 1 = 109, which is prime. a(6) = 9029 since 21^3 - T(21) - 1 = 9261 - 231 - 1 = 9029 which is prime. MAPLE KD:= proc() local a, b, d; a:= n^3; b:=(1/2)*n*(n+1); d:=a-b-1; if isprime(d) then RETURN(d): fi; end: seq(KD(), n=1..500); MATHEMATICA Select[Table[(n^3) - (n/2*(n + 1)) - 1, {n, 200}], PrimeQ] CROSSREFS Cf. A229157, A229080. Sequence in context: A141965 A141975 A142663 * A107155 A139504 A142798 Adjacent sequences: A229957 A229958 A229959 * A229961 A229962 A229963 KEYWORD nonn,less AUTHOR K. D. Bajpai, Oct 04 2013 STATUS approved

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Last modified August 9 08:50 EDT 2024. Contains 375035 sequences. (Running on oeis4.)