|
|
A292472
|
|
Generalized heptagonal numbers that are also Fibonacci numbers.
|
|
0
|
|
|
|
OFFSET
|
1,3
|
|
COMMENTS
|
Exactly five such numbers exist (cf. Srinivasa Rao, 2003).
All (generalized) g-gonal numbers in Fibonacci sequences up to g=20 have been determined (cf. Tengely, 2009). - Tomohiro Yamada, Sep 26 2017
|
|
LINKS
|
|
|
MATHEMATICA
|
Intersection[Array[(# (# + 1)/2 - 1)/5 &, 50, 0], Array[Fibonacci, 50, 0]] (* Michael De Vlieger, Sep 18 2017 *)
|
|
PROG
|
(PARI) a085787(n) = (5*(-n\2)^2 - (-n\2)*3*(-1)^n) / 2
is_a000045(n) = my(x=0); while(fibonacci(x) < n, x++); if(fibonacci(x)==n, return(1)); 0
for(n=0, 60, if(is_a000045(a085787(n)), print1(a085787(n), ", ")))
|
|
CROSSREFS
|
Cf. A292850 (Generalized heptagonal Lucas numbers).
|
|
KEYWORD
|
nonn,easy,fini,full
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|