

A215011


a(n) = least k>0 such that triangular(n) divides Fibonacci(k).


3



1, 4, 12, 15, 20, 8, 24, 12, 60, 10, 60, 84, 56, 40, 60, 18, 36, 36, 90, 120, 40, 120, 24, 300, 175, 252, 72, 168, 140, 60, 60, 60, 180, 360, 120, 228, 342, 252, 420, 60, 40, 88, 660, 60, 120, 48, 48, 168, 1400, 900, 252, 189, 108, 180, 120, 72, 252, 406, 1740
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OFFSET

1,2


COMMENTS

Triangular(n)=n*(n+1)/2 is the nth triangular number.


LINKS

Table of n, a(n) for n=1..59.


EXAMPLE

Triangular(2)=3, least k>0 such that 3 divides Fibonacci(k) is k=4, so a(2)=4.


PROG

(Python)
TOP = 333
prpr = y = 0
prev = k = 1
res = [1]*TOP
while y<TOP1:
for i in range(1, TOP):
if res[i]<0 and prev % (i*(i+1)/2) == 0:
res[i] = k
y += 1
curr = prpr+prev
prpr = prev
prev = curr
k += 1
for i in range(1, TOP):
print res[i],


CROSSREFS

Cf. A085779 (least k such that triangular(n) divides k!).
Cf. A001177 (least k such that n divides Fibonacci(k)).
Cf. A132632 (least k such that n^2 divides Fibonacci(k)).
Cf. A132633 (least k such that n^3 divides Fibonacci(k)).
Cf. A215453 (least k such that n^n divides Fibonacci(k)).
Cf. A214528 (least k such that n! divides Fibonacci(k)).
Cf. A000217, A000045.
Sequence in context: A260257 A256706 A103020 * A024353 A024354 A020883
Adjacent sequences: A215008 A215009 A215010 * A215012 A215013 A215014


KEYWORD

nonn


AUTHOR

Alex Ratushnyak, Aug 08 2012


STATUS

approved



