This site is supported by donations to The OEIS Foundation. Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A292472 Generalized heptagonal numbers that are also Fibonacci numbers. 0
 0, 1, 13, 34, 55 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS Intersection of A000045 and A085787. 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 B. Srinivasa Rao, Heptagonal Numbers in Fibonacci Sequence and Diophantine Equations 4x^2 = 5y^2(5y-3)^2+-16, The Fibonacci Quarterly, Vol. 41, No. 5 (2003), 414-420. Szabolcs Tengely, Finding g-gonal numbers in recurrence sequences, Fibonacci Quarterly, Vol.46/47, No. 3 (2009), 235-240. 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. A000045, A085787. Cf. A292850 (Generalized heptagonal Lucas numbers). Sequence in context: A245170 A134864 A093100 * A081271 A190458 A180673 Adjacent sequences:  A292469 A292470 A292471 * A292473 A292474 A292475 KEYWORD nonn,easy,fini,full AUTHOR Felix Fröhlich, Sep 17 2017 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified September 20 21:19 EDT 2019. Contains 327247 sequences. (Running on oeis4.)