|
Search: id:A034757
|
|
|
| A034757 |
|
a(1)=1, a(n) = smallest odd number such that all sums of pairs of (not necessarily distinct) terms in the sequence are distinct. |
|
+0
3
|
|
| 1, 3, 7, 15, 25, 41, 61, 89, 131, 161, 193, 245, 295, 363, 407, 503, 579, 721, 801, 949, 1129, 1185, 1323, 1549, 1643, 1831, 1939, 2031, 2317, 2623, 2789, 3045, 3143, 3641, 3791, 4057, 4507, 4757, 5019, 5559, 5849, 6309, 6707, 7181, 7593
(list; graph; listen)
|
|
|
OFFSET
|
0,2
|
|
|
COMMENT
|
a(1) = 1, a(n) = least number such that every difference a(i)-a(j) is a distinct even number. - Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Apr 07 2004
|
|
FORMULA
|
a(n) = 2*A005282(n)-1. (David Wasserman)
|
|
EXAMPLE
|
5 is not in the sequence since 5+1 is already obtainable from 3+3, 9 is excluded since 1, 3 and 7 are in the sequence, and would collide with 1+9
|
|
MATHEMATICA
|
seq2={1, 3}; Do[le=Length[seq2]; t=Last[seq2]+2; While[Length[Expand[(Plus @@ (x^seq2) + x^t)^2]] < Pochhammer[3, le]/le!, t=t+2]; AppendTo[seq2, t], {20}]; Print@seq2
|
|
CROSSREFS
|
Cf. A025582, A051912, A055598.
Adjacent sequences: A034754 A034755 A034756 this_sequence A034758 A034759 A034760
Sequence in context: A131753 A001213 A114221 this_sequence A078869 A011890 A131076
|
|
KEYWORD
|
nonn,nice,easy
|
|
AUTHOR
|
Wouter Meeussen (wouter.meeussen(AT)pandora.be), Jun 01 2000
|
|
EXTENSIONS
|
An incorrect comment from Amarnath Murthy (amarnath_murthy(AT)yahoo.com), also dated Apr 07 2004, has been deleted.
|
|
|
Search completed in 0.002 seconds
|
