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A087397 Smallest triangular number > 1 and == 1 (mod (prime(n)). 1
3, 10, 6, 15, 45, 66, 120, 153, 231, 378, 435, 630, 780, 861, 1035, 1326, 1653, 1770, 2145, 2415, 2556, 3003, 3321, 3828, 4560, 4950, 5151, 5565, 5778, 6216, 7875, 8385, 9180, 9453, 10878, 11175, 12090, 13041, 13695, 14706, 15753, 16110, 17955, 18336 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Robert Israel, Table of n, a(n) for n = 1..10000

FORMULA

a(n) = (prime(n)-2)*(prime(n)-1)/2 for n >= 3.

EXAMPLE

a(7) = 120 == 1 (mod 17), prime (7) = 17.

MAPLE

3, 10, seq((ithprime(i)-2)*(ithprime(i)-1)/2, i=3..50); # Robert Israel, Dec 23 2018

MATHEMATICA

Join[{3, 10}, Table[(Prime[n] - 2) (Prime[n] - 1) / 2, {n, 3, 50}]] (* Vincenzo Librandi, Dec 24 2018 *)

PROG

(MAGMA) [3, 10] cat [(NthPrime(n)-2)*(NthPrime(n)-1)/2: n in [3..50]]; // Vincenzo Librandi, Dec 24 2018

CROSSREFS

Sequence in context: A275741 A244846 A210415 * A210414 A289832 A196163

Adjacent sequences:  A087394 A087395 A087396 * A087398 A087399 A087400

KEYWORD

nonn

AUTHOR

Amarnath Murthy, Sep 10 2003

EXTENSIONS

More terms from David Wasserman, Jun 01 2005

Edited by Robert Israel, Dec 23 2018

STATUS

approved

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Last modified October 20 12:47 EDT 2019. Contains 328257 sequences. (Running on oeis4.)