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A289382
a(n) = 2^n mod triangular(n).
2
0, 1, 2, 6, 2, 1, 16, 4, 17, 34, 2, 40, 2, 4, 8, 120, 104, 1, 78, 46, 134, 70, 140, 16, 132, 121, 134, 30, 2, 94, 64, 400, 206, 429, 158, 334, 2, 4, 8, 616, 494, 1, 690, 346, 692, 142, 848, 64, 912, 1024, 8, 796, 797, 379, 1528, 4, 350, 178, 1418, 916, 2, 4, 512, 1056, 32, 2011
OFFSET
1,3
LINKS
FORMULA
a(n) = A000079(n) mod A000217(n) = 2^n mod n*(n+1)/2.
a(n) = 1 for n>1 in A272934. - Michel Marcus, Jul 04 2017
EXAMPLE
a(6) = 2**6 mod (6*7/2) = 64 mod 21 = 1.
MAPLE
seq(2^n mod n*(n+1)/2, n=1..100); # Robert Israel, Jul 04 2017
MATHEMATICA
Table[Mod[2^n, n (n + 1)/2], {n, 66}] (* Michael De Vlieger, Jul 04 2017 *)
PowerMod[2, #, (#(#+1))/2]&/@Range[70] (* Harvey P. Dale, Oct 12 2018 *)
PROG
(Python)
for n in range(1, 99): print(str(int(2**n % (n*(n+1)/2))), end=', ')
(PARI) a(n) = lift(Mod(2, n*(n+1)/2)^n); \\ Michel Marcus, Jul 04 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
Alex Ratushnyak, Jul 04 2017
STATUS
approved