A190220 -id:A190220 - cp's OEIS frontend

A190217 Numbers all of whose divisors are repdigit numbers.

1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 22, 33, 44, 55, 66, 77, 88, 99, 1111111111111111111, 2222222222222222222, 3333333333333333333, 4444444444444444444, 5555555555555555555, 6666666666666666666, 7777777777777777777, 8888888888888888888, 9999999999999999999

Offset: 1

Jaroslav Krizek, May 06 2011

Subset of A010785, A190220 and A190221.

			Number 99 is in sequence because all divisors of 99 (1, 3, 9, 11, 33, 99) are repdigit numbers.

A190219 Numbers all of whose divisors have decimal digits in strictly decreasing order.

Original entry on oeis.org

1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 21, 31, 40, 41, 43, 53, 61, 62, 63, 71, 73, 82, 83, 86, 93, 97, 421, 431, 521, 541, 631, 641, 643, 653, 743, 751, 761, 821, 842, 853, 862, 863, 941, 953, 961, 971, 983, 5431, 6421, 6521, 7321, 7541, 7621, 7643, 8431, 8521

Offset: 1

Jaroslav Krizek, May 06 2011

Sequence is finite. Last term a(104) = 98765431.

Subset of A009995 and A190220. Superset of A052014.

			Number 93 is in sequence because all divisors of 93 (1, 3, 31, 93) are numbers whose decimal digits are in strictly decreasing order.

Nathaniel Johnston, Table of n, a(n) for n = 1..104 (full sequence)

with(numtheory): A190219 := proc(n) option remember: local d,dd,i,j,k,m,poten: if(n=1)then return 1: fi: for k from procname(n-1)+1 do d:=divisors(k): poten:=1: for i from 1 to nops(d) do m:=-1: dd:=convert(d[i],base,10): for j from 1 to nops(dd) do if(mA190219(n),n=1..60); # Nathaniel Johnston, May 06 2011

Select[Range[9000],Max[Flatten[Differences/@(IntegerDigits/@Divisors[#])]]<0&] (* Harvey P. Dale, Feb 22 2024 *)

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A190217 Numbers all of whose divisors are repdigit numbers.

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A190219 Numbers all of whose divisors have decimal digits in strictly decreasing order.

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