OFFSET
1,2
COMMENTS
a(15) = 39 and a(16) = 217; when we write a(15) on top of a(16) we form the "brick":
.39
217
From left to right we read (vertically) the three integers 2, 31 and 97 which are prime and thus achieve a correct 2-integer brick.
LINKS
Eric Angelini, Another brick in the wall, Personal blog of the author, Feb. 2022.
EXAMPLE
a(1) = 1 and a(2) = 3 form the prime 13 when red vertically from left to right;
a(2) = 3 and a(3) = 7 form the prime 37 when red vertically from left to right;
a(3) = 7 and a(4) = 9 form the prime 79 when red vertically from left to right;
a(4) = 9 and a(5) = 27 form the primes 2 and 79 when red vertically from left to right;
a(5) = 27 and a(6) = 31 form the primes 23 and 71 when red vertically from left to right; etc.
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Eric Angelini and Carole Dubois, Feb 28 2022
STATUS
approved