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A158862 Prepending 3 to n-th triangular number produces a prime. 1
22, 46, 61, 82, 106, 118, 181, 286, 301, 373, 406, 433, 481, 493, 526, 562, 577, 661, 733, 802, 817, 886, 946, 961, 1033, 1162, 1177, 1246, 1258, 1261, 1297, 1342, 1426, 1513, 1546, 1558, 1573, 1618, 1741, 1813, 1822, 1846, 1873, 1882, 1918, 1921, 1957 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Or, concatenated T(2) and T(n) are prime. Or, concatenated A000217(2) and A000217(n) are prime.

LINKS

Table of n, a(n) for n=1..47.

EXAMPLE

n=22: T(2)=253, 3253 is prime,

n=46: T(46)=1081, 31081 is prime,

n=61: T(61)=1891, 31891 is prime.

CROSSREFS

A158844 Concatenated triangular numbers T (n), T(n + 1) and T(n + 2) are prime. A158845 Prepending 1 to n-th triangular number produces a prime. A158750 Concatenated triangular numbers that are prime. A000217 Triangular numbers.

Sequence in context: A106838 A190614 A281187 * A161666 A132763 A250723

Adjacent sequences:  A158859 A158860 A158861 * A158863 A158864 A158865

KEYWORD

base,nonn

AUTHOR

Zak Seidov, Mar 28 2009

STATUS

approved

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Last modified January 24 19:19 EST 2020. Contains 331211 sequences. (Running on oeis4.)