login
A113889
Smallest prime of the form: all sevens followed by prime(n); a(n) > prime(n); or 0 if no such prime exists.
0
0, 73, 0, 0, 77711, 77713, 7717, 719, 7723, 77777777777777777729, 77731, 777737, 7741, 743, 77747, 7753, 7759, 761, 77777777767, 7777777777771, 773, 777777777777777777777777777777777777777777777777777777777777777779
OFFSET
1,2
COMMENTS
Prime(n) is all zeros followed by prime(n).This is all sevens followed by prime(n). Conjecture: a(n) is nonzero if n >4.
The conjecture has been verified for n<100. - Joshua Albert (jba138(AT)psu.edu), Jan 20 2006
EXAMPLE
a(9) = 7723, as 723 is composite, prime(9) = 23.
MATHEMATICA
Join[{0, 73, 0, 0}, Flatten[Select[#, PrimeQ, 1]&/@Table[FromDigits[ PadLeft[ IntegerDigits[n], i, 7]], {n, Prime[Range[5, 30]]}, {i, IntegerLength[ n]+1, 100}]]] (* Harvey P. Dale, Nov 20 2013 *)
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Amarnath Murthy, Nov 18 2005
EXTENSIONS
More terms from Joshua Albert (jba138(AT)psu.edu), Jan 20 2006
STATUS
approved