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Search: a171666 -id:a171666
Displaying 1-2 of 2 results found.
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A171668
Fibonacci numbers sandwiched between two numbers having same number of divisors.
+10
2
34, 55, 144, 10946, 46368, 196418, 9227465, 1134903170, 4052739537881, 117669030460994, 420196140727489673, 12200160415121876738, 3928413764606871165730, 22698374052006863956975682, 68330027629092351019822533679447, 13598018856492162040239554477268290
(list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..70
MATHEMATICA
f[n_]:=Length[Divisors[n]]; lst={}; Do[fi=Fibonacci[n]; If[f[fi-1]==f[fi+1], AppendTo[lst, fi]], {n, 170}]; lst
CROSSREFS
Cf. A000005, A000045, A005237, A005238, A067889, A171666, A171667.
KEYWORD
nonn
AUTHOR
Vladimir Joseph Stephan Orlovsky, Dec 14 2009
EXTENSIONS
a(15)-a(16) from Amiram Eldar, Aug 08 2024
STATUS
approved
A171669
Pell numbers sandwiched between two numbers having same number of divisors.
+10
1
12, 5741, 2744210, 15994428, 21300003689580, 723573111879672, 1111984844349868137938112, 293199986221627877463941823267862, 9960168529794442859224531878561050, 27749033099085295754434173207717704165, 66992092050551637663438906713182313772
(list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..19
MATHEMATICA
f[n_]:=Length[Divisors[n]]; a=1; b=0; c=0; lst={}; Do[c=a+b+c; If[f[c-1]==f[c+1], AppendTo[lst, c]]; a=b; b=c, {n, 80}]; lst
CROSSREFS
Cf. A000005, A000129, A005237, A005238, A067889, A171666, A171667, A171668.
KEYWORD
nonn
AUTHOR
Vladimir Joseph Stephan Orlovsky, Dec 14 2009
EXTENSIONS
a(8)-a(11) from Amiram Eldar, Aug 08 2024
STATUS
approved
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Last modified March 1 06:15 EST 2025. Contains 381294 sequences.
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