|
|
A073640
|
|
a(1) = 2; a(n) = smallest prime greater than the previous term such that concatenation of two successive terms is a prime.
|
|
6
|
|
|
2, 3, 7, 19, 31, 37, 61, 73, 127, 139, 199, 211, 229, 283, 397, 433, 439, 463, 523, 541, 547, 577, 601, 607, 619, 739, 751, 787, 811, 919, 937, 991, 1009, 1021, 1039, 1093, 1201, 1213, 1297, 1447, 1453, 1459, 1471, 1483, 1657, 1663, 1723, 1783, 1867, 1879
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,1
|
|
LINKS
|
|
|
EXAMPLE
|
a(1)=2, the next prime is 3 and when 2 and 3 are concatenated we get 23, another prime. Hence a(2)=3. Likewise, a(3)=7 because 37 is prime, whereas the next prime after 3 is "5" which would lead to the nonprime "35".
|
|
MAPLE
|
pout := [2]: nout := [1]: for n from 2 to 1000 do: p := ithprime(n): d := parse(cat(pout[nops(pout)], p)): if (isprime(d)) then pout := [op(pout), p]: nout := [op(nout), n]: fi: od:
|
|
MATHEMATICA
|
t = {i = 2}; Do[While[! PrimeQ[FromDigits[Flatten[IntegerDigits[{Last[t], x = Prime[i]}]]]], i++]; AppendTo[t, x], {49}]; t (* Jayanta Basu, Jul 03 2013 *)
|
|
CROSSREFS
|
|
|
KEYWORD
|
base,nonn
|
|
AUTHOR
|
|
|
EXTENSIONS
|
More terms from Mark Hudson (mrmarkhudson(AT)hotmail.com), Jan 31 2003
|
|
STATUS
|
approved
|
|
|
|