|
Search: id:A088614
|
|
|
| A088614 |
|
Alternate prime and composite numbers not included earlier such that every partial concatenation is a prime: a(2n) is composite and a(2n-1) is prime. |
|
+0
4
|
|
| 2, 9, 3, 27, 11, 51, 13, 33, 41, 93, 31, 99, 29, 63, 1117, 441, 503, 303, 163, 171, 59, 357, 67, 219, 113, 417, 691, 729, 239, 511, 227, 393, 211, 189, 3797, 291, 1789, 549, 419, 501, 103, 81, 3257, 39, 727, 531, 617, 69, 6883, 387, 521, 153, 1237, 287, 3391, 927
(list; graph; listen)
|
|
|
OFFSET
|
1,1
|
|
|
COMMENT
|
Conjecture: 1 and 5 are the only two odd nonmembers.
|
|
EXAMPLE
|
2,29,293,29327,...etc. are primes.
|
|
MATHEMATICA
|
p = Prime[ Range[ 1000]]; np = Complement[ Range[ 1000], p]; a[n_] := a[n] = Block[{k = 1, q = Flatten[ IntegerDigits[ # ] & /@ Table[ a[i], {i, n - 1}]]}, If[ OddQ[n], While[ !PrimeQ[ FromDigits[ Join[q, IntegerDigits[ p[[k]] ]]]], k++ ]; q = p[[k]]; p = Delete[p, k]; q, While[ !PrimeQ[ FromDigits[ Join[q, IntegerDigits[ np[[k]] ]]]], k++ ]; q = np[[k]]; np = Delete[np, k]; q]]; Table[ a[n], {n, 56}] (from Robert G. Wilson v Apr 23 2004)
|
|
CROSSREFS
|
Cf. A088615.
Sequence in context: A074948 A011385 A163907 this_sequence A162615 A155163 A161934
Adjacent sequences: A088611 A088612 A088613 this_sequence A088615 A088616 A088617
|
|
KEYWORD
|
base,nonn
|
|
AUTHOR
|
Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Oct 16 2003
|
|
EXTENSIONS
|
More terms from Ray Chandler (rayjchandler(AT)sbcglobal.net), Oct 18 2003
|
|
|
Search completed in 0.002 seconds
|
