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A352017
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).
1
1, 2, 7, 21, 9, 3, 27, 33, 39, 17, 11, 239, 13, 37, 19, 77, 31, 99, 71, 79, 231, 91, 73, 211, 93, 97, 213, 313, 331, 111, 113, 337, 119, 117, 2331, 179, 131, 339, 171, 139, 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
OFFSET
1,2
LINKS
Eric Angelini, Another brick in the wall, Personal blog of the author, Feb. 2022.
EXAMPLE
a(1) = 1, a(2) = 2 and a(3) = 7 stacked form the prime number 127, which is what we want;
a(2) = 2, a(3) = 7 and a(4) = 21 stacked form the hereunder "brick":
.2
.7
21
From left to right we read (vertically) the two integers 2 and 271 which are prime and thus achieve a correct 3-integer brick;
a(3) = 7, a(4) = 21 and a(5) = 9 stacked form the hereunder "brick":
.7
21
.9
From left to right we read (vertically) the two integers 2 and 719 which are prime and thus achieve a correct 3-integer brick;
(...)
a(n) = 1739, a(n+1) = 997 and a(n+2) = 1771 stacked form the hereunder "brick":
1739
.997
1771
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.
CROSSREFS
Cf. A352016 (2-integer bricks).
Sequence in context: A139012 A132605 A088157 * A265316 A079034 A265500
KEYWORD
base,nonn
AUTHOR
Carole Dubois and Eric Angelini, Feb 28 2022
STATUS
approved