A322570 Positive integers k such that A270710(k) (= (k+1)*(3*k-1)) have only 1 or 2 different digits in base 10.

1, 2, 3, 4, 5, 6, 12, 16, 17, 33, 34, 48, 54, 285, 333, 334, 365, 385, 430, 471, 516, 816, 1049, 3333, 3334, 33333, 33334, 333333, 333334, 483048, 3333333, 3333334, 33333333, 33333334, 333333333, 333333334, 3333333333, 3333333334, 33333333333, 33333333334

Offset

1,2

Links

Giovanni Resta, Table of n, a(n) for n = 1..50

Formula

For k > 0, A002277(k) is a term.

For k >= 0, A002277(k) + 1 (= A093137(k)) is a term.

Mathematica

Select[Range@ 50000, Length@ Union@ IntegerDigits[3 #^2 + 2 # - 1] <= 2 &] (* Giovanni Resta, Sep 04 2019 *)

Prog

(PARI) for(k=1, 1e8, if(#Set(digits(3*k^2+2*k-1))<=2, print1(k", ")))
(Magma) [k:k in [1..10000000]| #Set(Intseq((k+1)*(3*k-1))) le 2]; // Marius A. Burtea, Aug 29 2019

Crossrefs

Cf. A002277, A016069, A093137, A213517 (in case of triangular numbers), A270710, A322571.

Sequence in context: A023788 A032989 A367147 * A108320 A177958 A032941

Adjacent sequences: A322567 A322568 A322569 * A322571 A322572 A322573

Keyword

nonn,base

Author

Seiichi Manyama, Aug 29 2019

Extensions

a(35)-a(36) from Jinyuan Wang, Aug 30 2019

a(37)-a(40) from Giovanni Resta, Sep 04 2019

Status

approved