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A254957
Triangular numbers n with digits d_1, d_2, ..., d_k such that d_1*(d_1+1)/2 + ... + d_k*(d_k+1)/2 is a triangular number.
0
0, 1, 3, 6, 10, 136, 231, 300, 3160, 3741, 4371, 5565, 5995, 6328, 6555, 10011, 10440, 10731, 13366, 13530, 14196, 18528, 19900, 20301, 21115, 23220, 25200, 25651, 30135, 30628, 30876, 32385, 34716, 37401, 42778, 43071, 46971, 47278, 53301, 60031, 60378, 63903, 64620, 69378, 74691, 86320, 89253, 90525
OFFSET
1,3
PROG
(PARI) istri(n)=for(k=0, n+1, if(k*(k+1)/2==n, return(1))); 0
for(n=0, 10^3, N=n*(n+1)/2; d=digits(N); s=0; for(i=1, #d, s+=d[i]*(d[i]+1)/2); if(istri(s), print1(N, ", ")))
CROSSREFS
Sequence in context: A354000 A368173 A125567 * A124266 A137941 A353998
KEYWORD
nonn,base
AUTHOR
Derek Orr, Feb 11 2015
STATUS
approved