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A115887 Triangular numbers equal to the difference between a prime number and its index. 2
1, 3, 6, 10, 28, 105, 120, 153, 231, 465, 496, 1081, 1378, 1485, 1653, 1711, 2628, 3003, 3081, 3160, 4950, 5050, 5460, 6670, 6903, 8001, 8778, 10296, 11781, 14028, 15225, 16290, 19701, 20503, 21528, 21945, 22155, 24310, 24531, 25200, 27495 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Harvey P. Dale, Table of n, a(n) for n = 1..500

EXAMPLE

28=T(7)=p(13)-13.

MATHEMATICA

Union[Select[Table[Prime[i]-i, {i, 20000}], IntegerQ[Sqrt[8#+1]]&]] (* Harvey P. Dale, Jun 28 2012 *)

CROSSREFS

Cf. A115883.

Sequence in context: A110891 A197435 A240514 * A068195 A080506 A109163

Adjacent sequences:  A115884 A115885 A115886 * A115888 A115889 A115890

KEYWORD

nonn

AUTHOR

Giovanni Resta, Feb 06 2006

STATUS

approved

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Last modified November 18 14:59 EST 2019. Contains 329262 sequences. (Running on oeis4.)