A352017 - OEIS

%I #5 Mar 13 2022 19:25:40

%S 1,2,7,21,9,3,27,33,39,17,11,239,13,37,19,77,31,99,71,79,231,91,73,

%T 211,93,97,213,313,331,111,113,337,119,117,2331,179,131,339,171,139,

%U 333,177,133,393,771,311,993,711,191,913,197,173,319,797,317,2313,733,371,391,773,377,933,739,717,2311,939,713

%N Lexicographically earliest sequence of distinct positive integers such that a(n) written on top of a(n+1) which in turn is written on top of a(n+2) form a correct 3-integer brick (see the Comments and Example sections for an explanation).

%H Eric Angelini, <a href="http://cinquantesignes.blogspot.com/2022/02/another-brick-in-wall.html">Another brick in the wall</a>, Personal blog of the author, Feb. 2022.

%e a(1) = 1, a(2) = 2 and a(3) = 7 stacked form the prime number 127, which is what we want;

%e a(2) = 2, a(3) = 7 and a(4) = 21 stacked form the hereunder "brick":

%e .2

%e .7

%e 21

%e From left to right we read (vertically) the two integers 2 and 271 which are prime and thus achieve a correct 3-integer brick;

%e a(3) = 7, a(4) = 21 and a(5) = 9 stacked form the hereunder "brick":

%e .7

%e 21

%e .9

%e From left to right we read (vertically) the two integers 2 and 719 which are prime and thus achieve a correct 3-integer brick;

%e (...)

%e a(n) = 1739, a(n+1) = 997 and a(n+2) = 1771 stacked form the hereunder "brick":

%e 1739

%e .997

%e 1771

%e From left to right we read (vertically) the four integers 11, 797, 397 and 971 which are prime and thus achieve a correct 3-integer brick; etc.

%Y Cf. A352016 (2-integer bricks).

%K base,nonn

%O 1,2

%A _Carole Dubois_ and _Eric Angelini_, Feb 28 2022