A072725 -id:A072725 - cp's OEIS frontend

A072723 Integers which are exactly the concatenation of the first m odd numbers (A019519) divided by their sum (A000290 = m^2).

1, 15, 16764334957, 3079163563531047898532266016633501

Offset: 1

Henry Bottomley, Jul 06 2002

A probability argument suggests that this sequence may be finite.

			a(1) = 1/1 = 1; a(2) = 135/(1+3+5) = 15; a(3) = 1357911131517/(1+3+5+7+9+11+13+15+17) = 16764334957; a(4) = 1357911131517192123252729313335373941/(1+3+5+7+9+11+13+15+17+19+21+23+25+27+29+31+33+35+37+39+41) = 3079163563531047898532266016633501.

Cf. A067122, A072724, A072725.

Select[Table[FromDigits[Flatten[IntegerDigits/@Range[1,2n+1,2]]]/Total[Range[1,2n+1,2]],{n,0,30}],IntegerQ] (* Harvey P. Dale, Mar 24 2023 *)

A072724 Integers which are exactly the concatenation of the first m even numbers (A019520) divided by their sum (A002378 = m^2+m).

Original entry on oeis.org

1, 4, 8227, 3427918353

Offset: 1

Henry Bottomley, Jul 06 2002

A probability argument suggests that this sequence may be finite.

			a(1) = 2/2 =1; a(2) = 24/(2+4) = 4; a(3) = 246810/(2+4+6+8+10) = 8227; a(4) = 246810121416/(2+4+6+8+10+12+14+16).

Cf. A067121, A072723, A072725.

With[{eds=Range[2,1500,2]},Select[Table[FromDigits[Flatten[ IntegerDigits/@ Take[eds,n]]]/Total[Take[eds,n]],{n,502}],IntegerQ]] (* Harvey P. Dale, Nov 29 2011 *)

cp's OEIS Frontend

A072723 Integers which are exactly the concatenation of the first m odd numbers (A019519) divided by their sum (A000290 = m^2).

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