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, 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

Links

Table of n, a(n) for n=1..48.

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

Cf. A000217, A254956.

Sequence in context: A354000 A368173 A125567 * A124266 A137941 A353998

Adjacent sequences: A254954 A254955 A254956 * A254958 A254959 A254960

Keyword

nonn,base

Author

Derek Orr, Feb 11 2015

Status

approved