|
| |
|
|
A133198
|
|
Triangular numbers such that moving the last digit to the front produces a square number.
|
|
0
| |
|
|
1, 10, 3240, 464166, 1043290, 5740966, 335936160, 428264011, 3529890253, 4015289691, 108170400250, 821266581691, 2216062991691, 34830532944360, 2453718234672253, 6017966241009003, 11215323437683690, 214486304402280015, 446417240103777645
(list; graph; refs; listen; history; internal format)
|
|
|
|
OFFSET
| 1,2
|
|
|
EXAMPLE
| 3240 is a triangular number, 0324 is a square number - hence 3240 belongs to this sequence.
|
|
|
MAPLE
| a:=proc(n) local n2, L: n2:=convert((1/2)*n*(n+1), base, 10): L:=nops(n2): if type(sqrt((1/20)*n*(n+1)-(1/10)*n2[1]+n2[1]*10^(L-1)), integer)=true then (1/2)*n*(n+1) else end if end proc: seq(a(n), n=1..10^7); - Emeric Deutsch (deutsch(AT)duke.poly.edu), Oct 17 2007
|
|
|
MATHEMATICA
| Select[Table[n(n + 1)/2, {n, 1000000}], IntegerQ[Sqrt[ FromDigits[ Prepend[Drop[IntegerDigits[ # ], -1], Last[IntegerDigits[ # ]]]]]] &]
|
|
|
CROSSREFS
| Sequence in context: A132675 A123377 A061543 * A001329 A007101 A007103
Adjacent sequences: A133195 A133196 A133197 * A133199 A133200 A133201
|
|
|
KEYWORD
| base,nonn
|
|
|
AUTHOR
| Tanya Khovanova (tanyakh(AT)yahoo.com), Oct 09 2007
|
|
|
EXTENSIONS
| More terms from Emeric Deutsch (deutsch(AT)duke.poly.edu), Oct 17 2007
Offset corrected and a(15)-a(19) from Donovan Johnson (donovan.johnson(AT)yahoo.com), Jan 31 2011
|
| |
|
|
