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A078256
Triangular numbers in which frequency of occurrence of every digit is same.
1
0, 1, 3, 6, 10, 15, 21, 28, 36, 45, 55, 66, 78, 91, 105, 120, 136, 153, 190, 210, 231, 253, 276, 325, 351, 378, 406, 435, 465, 496, 528, 561, 630, 666, 703, 741, 780, 820, 861, 903, 946, 1035, 1275, 1326, 1378, 1485, 1540, 1596, 1653, 1830, 1953, 2016, 2145
OFFSET
1,3
LINKS
MATHEMATICA
T[n_] := n*(n + 1)/2; f[n_] := Block[{dc = DigitCount[n], s}, s = Select[dc, Positive]; Min @@ s == Max @@ s]; Select[Array[T, 70, 0], f] (* Ray Chandler, May 11 2007 *)
PROG
(PARI) \\ here isok(k) tests if each digit k has equal frequency.
isok(k)={my(f=vector(10)); foreach(digits(k), t, f[1+t]++); my(c=vecmax(f)); 0==#select(t->t>0&&t<c, f)}
lista(n)={my(L=List(), k=0); while(#L<n, my(t=k*(k+1)/2); if(isok(t), listput(L, t)); k++); Vec(L)} \\ Andrew Howroyd, Sep 21 2024
CROSSREFS
Sequence in context: A109811 A025747 A025738 * A025731 A077367 A077366
KEYWORD
base,easy,nonn
AUTHOR
Amarnath Murthy, Nov 24 2002
EXTENSIONS
Offset changed by Andrew Howroyd, Sep 21 2024
STATUS
approved