|
Search: id:A003679
|
|
|
| A003679 |
|
Numbers that are not the sum of 3 pentagonal numbers.
(Formerly M3323)
|
|
+0
7
|
|
| 4, 8, 9, 16, 19, 20, 21, 26, 30, 31, 33, 38, 42, 43, 50, 54, 55, 60, 65, 67, 77, 81, 84, 88, 89, 90, 96, 99, 100, 101, 111, 112, 113, 120, 125, 131, 135, 138, 142, 154, 159, 160, 166, 170, 171, 183, 195, 204, 205, 207, 217, 224, 225, 226, 229, 230, 236, 240, 241
(list; graph; listen)
|
|
|
OFFSET
|
1,1
|
|
|
COMMENT
|
Guy's paper says that the sequence probably contains exactly 210 terms, six of which require five pentagonal numbers: 9, 21, 31, 43, 55, and 89. The last term is conjectured to be 33066. - T. D. Noe (noe(AT)sspectra.com), Apr 19 2006
|
|
REFERENCES
|
R. K. Guy, Every number is expressible as the sum of how many polygonal numbers?, Amer. Math. Monthly 101 (1994), 169-172.
|
|
LINKS
|
T. D. Noe, Table of n, a(n) for n = 1..210
Eric Weisstein's World of Mathematics, Pentagonal Number
|
|
MATHEMATICA
|
nn=200; pen=Table[n(3n-1)/2, {n, 0, nn-1}]; lst=Range[pen[[ -1]]; Do[n=pen[[i]]+pen[[j]]+pen[[k]]; If[n<=pen[[ -1]], lst=DeleteCases[lst, n]]], {i, nn}, {j, i, nn}, {k, j, nn}]; lst - T. D. Noe (noe(AT)sspectra.com), Apr 19 2006
|
|
CROSSREFS
|
Cf. A117065 (primes in this sequence).
Adjacent sequences: A003676 A003677 A003678 this_sequence A003680 A003681 A003682
Sequence in context: A090779 A034038 A069265 this_sequence A079432 A134344 A119315
|
|
KEYWORD
|
nonn,easy,nice
|
|
AUTHOR
|
njas, Mira Bernstein
|
|
|
Search completed in 0.002 seconds
|
