A242957 Consider a number n with m decimal digits. The sequence lists the numbers n having the suffix of length m-1 in the middle of the decimal expansion of prime(n).

33, 55, 56, 80, 81, 82, 83, 109, 278, 287, 897, 898, 899, 910, 912, 915, 917, 918, 919, 920, 921, 939, 941, 945, 948, 2004, 3004, 3005, 4008, 4009, 5006, 6003, 6455, 6456, 6457, 6459, 6460, 6466, 7007, 8009, 9001, 10053, 20053, 46321, 50021, 60078, 70027, 74685

Offset

1,1

Comments

The corresponding primes are 137, 257, 263, 409, 419, 421, 431, 599, 1789, 1873, 6977, 6983, 6991, 7103, 7121, 7151, 7177, 7187, ...

Links

Table of n, a(n) for n=1..48.

Example

287 is in the sequence because prime(287) = 1873 and the suffix 87 is in the middle of the decimal expansion of 1873.

Mathematica

lst={}; Do[a=IntegerDigits[Prime[n]]; b=Length[a]; l=IntegerLength[n]-1; c=IntegerLength[Mod[n, 10^l]]; If[Mod[n, 10^l]==0, c=1]; If[EvenQ[b-c]&&FromDigits[Take[a, {(b-c)/2+1, (b+c)/2}]]==Mod[n, 10^l], AppendTo[lst, n]], {n, 26, 10^5}]; lst

Crossrefs

Cf. A242956.

Sequence in context: A211141 A007373 A229254 * A024628 A061864 A075810

Adjacent sequences: A242954 A242955 A242956 * A242958 A242959 A242960

Keyword

nonn,base

Author

Michel Lagneau, May 27 2014

Status

approved