A372336 -id:A372336 - cp's OEIS frontend

A372335 For a positive number k, let L(k) denote the list consisting of k followed by the prime factors of k, with repetition, in nondecreasing order; sequence gives composite k such that the digits of L(k) alternate being larger than and then smaller than the previous digit.

14, 15, 78, 161, 591, 1214, 1317, 1318, 1326, 1407, 1418, 1438, 1506, 1509, 1514, 1527, 1538, 1618, 1626, 1646, 1658, 1703, 1714, 1718, 1734, 1739, 1758, 1814, 1834, 1838, 1839, 1857, 1858, 1934, 1938, 2307, 2427, 2509, 2517, 2534, 2535, 2715, 2757, 2758, 2869, 2958, 3419, 3439, 3514, 3523

Offset: 1

Scott R. Shannon, Apr 28 2024

No term can end in 0 or 2; a number ending in 2 would mean the first prime factor is 2, which would disqualify the number, while a number ending in 0 would mean the first 3 distinct prime factors would have to be 2, 3, 5 or 2, 5, either of which would also disqualify the number.

			161 is a term as 161 = 7 * 23 which when concatenated give "161723", the digits of which alternate from being larger than and then smaller than the previous digit.

Scott R. Shannon, Table of n, a(n) for n = 1..10000

Cf. A372336, A372280, A372308, A372034, A372029, A056704.

cp's OEIS Frontend

A372335 For a positive number k, let L(k) denote the list consisting of k followed by the prime factors of k, with repetition, in nondecreasing order; sequence gives composite k such that the digits of L(k) alternate being larger than and then smaller than the previous digit.

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