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A078723
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Prime(n*(n+1)/2 + n).
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1
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3, 11, 23, 43, 71, 103, 149, 193, 251, 313, 389, 463, 569, 653, 761, 881, 1013, 1129, 1289, 1451, 1601, 1777, 1979, 2143, 2357, 2591, 2789, 3023, 3301, 3539, 3793, 4057, 4349, 4651, 4969, 5297, 5639, 5927, 6299, 6673
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,1
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COMMENTS
| The sum of the reciprocals appears to converge.
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FORMULA
| a(n) = A000040(A000096(n)).
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MATHEMATICA
| Table[Prime[(n(n+1))/2+n], {n, 50}] [From Harvey P. Dale, Jan 04 2011]
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PROG
| (PARI) triprimes(n) = { sr = 0; for(j=1, n, x = j*(j+1)/2 +j; z = prime(x); sr+=1.0/z; print1(z" "); ); print(); print(sr); }
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CROSSREFS
| Primes in second diagonal from right in triangle in A078721.
Sequence in context: A121509 A096071 A159791 * A141187 A107138 A145473
Adjacent sequences: A078720 A078721 A078722 * A078724 A078725 A078726
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KEYWORD
| easy,nonn
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AUTHOR
| Cino Hilliard (hillcino368(AT)gmail.com), Dec 20 2002
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