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Search: id:A152899
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| A152899 |
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Triangular numbers t such that (t-1)/2, (t+1)/2, 2t-1 or 2t+1 is prime. |
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+0
2
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| 1, 3, 6, 10, 15, 21, 36, 45, 55, 66, 78, 91, 105, 120, 136, 153, 190, 210, 231, 253, 300, 325, 351, 378, 406, 465, 496, 561, 630, 741, 780, 861, 990, 1035, 1081, 1176, 1225, 1275, 1431, 1485, 1540, 1596, 1653, 1770, 1830, 1953, 2080, 2145, 2211, 2346, 2415
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OFFSET
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1,2
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COMMENT
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These numbers are the t in sequence A152900, sorted and uniqued. It is not possible for all four numbers to be prime because when t is odd either (t-1)/2 or (t+1)/2 must be even.
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EXAMPLE
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10 is here because 19 is prime. 15 is here because 7, 29 and 31 are prime.
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MATHEMATICA
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nn=100; Select[Range[nn]*Range[2, 1+nn]/2, PrimeQ[(#-1)/2] || PrimeQ[(#+1)/2] || PrimeQ[2#-1] || PrimeQ[2#+1] &]
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CROSSREFS
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A137446
Sequence in context: A025745 A101551 A051166 this_sequence A061304 A147846 A109442
Adjacent sequences: A152896 A152897 A152898 this_sequence A152900 A152901 A152902
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KEYWORD
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nonn
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AUTHOR
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T. D. Noe (noe(AT)sspectra.com), Dec 14 2008
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