A213310 Numbers with exactly 3 nonprime substrings (substrings with leading zeros are considered to be nonprime).

10, 14, 16, 18, 40, 44, 46, 48, 49, 60, 64, 66, 68, 69, 80, 81, 84, 86, 88, 90, 91, 94, 96, 98, 99, 117, 123, 127, 132, 133, 135, 139, 153, 157, 167, 171, 172, 175, 177, 193, 211, 213, 217, 222, 225, 230, 234, 236, 238, 241

Offset

1,1

Comments

The sequence is finite. Proof: Each 6-digit number has at least 4 nonprime substrings. Thus, each number with more than 6 digits has >= 4 nonprime substrings, too. Consequently, there is a boundary b<10^5, such that all numbers > b have more than 3 nonprime substrings.

The first term is a(1)=10=A213302(3). The last term is a(310)=73373=A213300(3).

Links

Hieronymus Fischer, Table of n, a(n) for n = 1..310

Example

a(1)=10, since 10 has 3 nonprime substrings (0, 1, 10).
a(310)= 73373, since there are 3 nonprime substrings (33, 7337 and 73373).

Crossrefs

Cf. A019546, A035232, A039996, A046034, A069489, A085823, A211681, A211682, A211684, A211685.

Cf. A035244, A079307, A213300 - A213321.

Sequence in context: A330210 A067188 A092632 * A055197 A116610 A289698

Adjacent sequences: A213307 A213308 A213309 * A213311 A213312 A213313

Keyword

nonn,fini,base

Author

Hieronymus Fischer, Aug 26 2012

Status

approved