|
Search: id:A094044
|
|
|
| A094044 |
|
Alternate prime and composite numbers not included earlier such that every concatenation of a pair of terms is a prime: a(2n) is nonprime and a(2n-1) is prime. |
|
+0
2
|
|
| 2, 9, 7, 1, 3, 49, 19, 33, 13, 21, 11, 51, 47, 87, 31, 63, 17, 77, 23, 39, 29, 27, 41, 57, 37, 69, 59, 81, 61, 99, 67, 91, 73, 93, 43, 117, 79, 111, 71, 119, 53, 129, 83, 177, 89, 123, 113, 143, 107, 171, 103, 141, 97, 159, 157, 133, 109, 121, 139, 169, 151, 153, 137, 147
(list; graph; listen)
|
|
|
OFFSET
|
1,1
|
|
|
COMMENT
|
Conjecture: 5 is the only nonmember.
|
|
EXAMPLE
|
a(3)=7 => 97 is a prime but not necessarily 297 (in fact not a prime).
|
|
MATHEMATICA
|
p = Prime[ Range[ 500]]; np = Drop[ Complement[ Range[ 500], p], 1]; a[0] = 0; a[n_] := a[n] = Block[{k = 1, q = IntegerDigits[a[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, 64}]
|
|
CROSSREFS
|
Cf. A088614, A094045.
Sequence in context: A009306 A021775 A016596 this_sequence A011070 A013500 A021340
Adjacent sequences: A094041 A094042 A094043 this_sequence A094045 A094046 A094047
|
|
KEYWORD
|
nonn,base
|
|
AUTHOR
|
Robert G. Wilson v (rgwv(AT)rgwv.com), Apr 23 2004
|
|
|
Search completed in 0.002 seconds
|
