A290224 Numbers n such that A290223(n) = 0.

1, 19, 81, 162, 181, 199, 243, 262, 324, 343, 405, 424, 486, 505, 567, 648, 685, 729, 766, 810, 847, 891, 910, 928, 972, 1053, 1072, 1134, 1153, 1215, 1234, 1296, 1315, 1377, 1458, 1495, 1539, 1576, 1620, 1657, 1701, 1720, 1738, 1782, 1801, 1819, 1863, 1944, 1981, 1999, 2025, 2044, 2106, 2125, 2187, 2206, 2268

Offset

1,2

Comments

This sequence is believed to be infinite.

Links

Table of n, a(n) for n=1..57.

Example

181 is in this sequence because 181 - (1+8+1)^2 = 81. Then 81 - (8+1)^2 = 0.

Prog

(PARI)
a(n)=k=n; c=1; v=List(); listput(v, k); while(c, if(k>=0, k-=sumdigits(k)^2; c+=1; if(k==2||k==3||k==0||k==6||k==9, return(k)); if(vecsearch(Vec(v), k), return(sumdigits(abs(k)))); listput(v, k)); if(k<0, k+=sumdigits(-k)^2; c+=1; if(k==2||k==3||k==0||k==6||k==9, return(k)); if(vecsearch(Vec(v), k), return(sumdigits(abs(k)))); listput(v, k)); c+=1)
for(n=1, 10^4, if(a(n)==0, print1(n, ", ")))

Crossrefs

Cf. A007953, A003132, A290223.

Sequence in context: A366965 A172973 A212056 * A071633 A334086 A217052

Adjacent sequences: A290221 A290222 A290223 * A290225 A290226 A290227

Keyword

nonn,base

Author

Derek Orr, Jul 24 2017

Status

approved