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Search: id:A078721
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| 2, 3, 7, 17, 31, 53, 79, 109, 157, 199, 263, 331, 401, 479, 577, 661, 773, 887, 1021, 1153, 1297, 1459, 1609, 1787, 1993, 2161, 2377, 2609, 2797, 3041, 3313, 3547, 3803, 4079, 4363, 4663, 4987, 5309, 5647, 5953, 6311, 6689, 7027, 7481, 7841, 8263, 8689
(list; graph; listen)
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OFFSET
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0,1
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COMMENT
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Primes on the left side of the of the triangle formed by listing successively the prime numbers in a triangular grid:
........ 2
....... 3 5
..... 7 11 13
... 17 19 23 29
.. 31 37 41 43 47
. 53 59 61 67 71 73
The sum of the reciprocals appears to converge. The PARI program is limited to n <= 6000.
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PROGRAM
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(PARI) triprimes(n) = { sr = 0; for(j=0, n, x = j*(j+1)/2+1; z = prime(x); sr+=1.0/z; print1(z" "); ); print(); print(sr); }
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CROSSREFS
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Cf. A011756, A078722, A078723, etc.
Sequence in context: A110480 A083822 A030086 this_sequence A077007 A105554 A135364
Adjacent sequences: A078718 A078719 A078720 this_sequence A078722 A078723 A078724
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KEYWORD
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easy,nonn
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AUTHOR
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Cino Hilliard (hillcino368(AT)gmail.com), Dec 20 2002
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