1,4

a(4)=8 because the first three prime n, concatenated, are 2+3+5+7 or 2357. There are 8 prime arrangements: 2357 2753 3257 3527 5237 5273 7253 7523.

A054260, A053160, A053161.

Sequence in context: A085353 A125396 A163444 this_sequence A099335 A132506 A080270

Adjacent sequences: A053092 A053093 A053094 this_sequence A053096 A053097 A053098

base,easy,nonn

Enoch Haga (Enokh(AT)comcast.net), Mar 19 2000